# Chemistry Figures: linking to an exact figure

> Chemistry Figures (https://chemistryfigures.com) is a free set of generators that make clean, printable chemistry figures for teachers to put in tests, worksheets and slides: lab instruments showing a reading for students to read (graduated cylinders, burets, beakers, gas syringes, rulers, balances, thermometers, pH meters and pH paper), titration curves, particle diagrams, Bohr models, Lewis structures and orbital diagrams. There is no account or sign-up. It is part of STEM Figures (https://stemfigures.com), with sister sites Math Figures (https://mathfigures.com) and Physics Figures (https://physicsfigures.com).

- Each generator is one page that draws one kind of figure from the settings a teacher picks. Figures are drawn in the browser; nothing to install.
- Every setting is kept in the page address (the URL query string), so a link with parameters opens that exact figure. The page’s Share link button copies it.
- Parameters left out of a link take their default values. A value the page doesn’t understand is ignored, and numbers are clamped and rounded to what the instrument can show, so a link always opens a figure.
- A figure can be copied to the clipboard as an image, downloaded as a PNG (at 3× size, sharp in print) or as an SVG, or printed: printing the page prints just the figure, 7.5 inches wide.
- Most figures have an optional chart title and an optional answer key line printed under them, so one figure can serve as the question and the key.
- Teachers can undo and redo changes and save named presets, which stay in their own browser.

## How to build a link

- A link to an exact figure is the generator’s address followed by ? and its parameters, joined by &, e.g. https://chemistryfigures.com/volume-reading?instrument=buret&reading=23.47.
- Give only the parameters that differ from the defaults. Encode values as usual for a URL: a space as + or %20, a plus sign as %2B, and JSON values percent-encoded.
- On/off parameters are 1 or 0. Choices are the exact lowercase words listed for each parameter.
- The same reference for people, with clickable examples: https://chemistryfigures.com/linking

## Volume Reading

https://chemistryfigures.com/volume-reading

Make printable graduated cylinder, buret and beaker figures for chemistry tests. Type a volume and students read it from the meniscus, with a magnified view for the estimated digit.

Pick the instrument with instrument (and its size with size or beaker), and the volume it shows with reading, in mL. The reading is rounded to one digit past the smallest mark and kept on the scale.

### Parameters

- instrument (choice: cylinder, buret, beaker. cylinder: graduated cylinder; buret: 50 mL buret; beaker: beaker; default cylinder): The volume instrument drawn.
- size (choice: 10, 25, 50, 100, 250, 1000; default 100; used when instrument=cylinder): The graduated cylinder’s capacity in mL.
- beaker (choice: small, medium, large. small 50 mL, medium 250 mL, large 600 mL; default medium; used when instrument=beaker): The beaker’s size.
- reading (number: 0 to 1000. Rounded and kept within the instrument’s scale (see notes); default 43.6): The volume the liquid shows, in mL, read at the bottom of the meniscus.
- view (choice: both, magnifier, whole. both: the instrument with a magnified circle of its scale beside it; magnifier: the magnified circle alone; whole: the instrument alone; default both; used when instrument is cylinder or buret): What the figure shows for a cylinder or buret.
- beakerView (choice: both, magnifier, whole. both: the instrument with a magnified circle of its scale beside it; magnifier: the magnified circle alone; whole: the instrument alone; default whole; used when instrument=beaker): What the figure shows for a beaker.
- span (number: 1 to 6; default 3; used when view=both or view=magnifier): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- tint (choice: gray, blue, red, green; default gray): The liquid’s color. Gray photocopies best.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “Reading: 43.6 mL”.

### Rules between parameters

- size applies only to the graduated cylinder and beaker only to the beaker; a buret is always 50 mL and reads from 0 at the top.
- reading is rounded and clamped to the chosen instrument: cylinder 10: 0–10 mL to 2 decimal places; cylinder 25: 0–25 mL to 2 decimal places; cylinder 50: 0–50 mL to 1 decimal place; cylinder 100: 0–100 mL to 1 decimal place; cylinder 250: 10–250 mL to 1 decimal place; cylinder 1000: 0–1000 mL to whole mL; buret: 0–50 mL to 2 decimal places; beaker small: 0–50 mL to whole mL; beaker medium: 0–250 mL to whole mL; beaker large: 0–600 mL to whole mL.
- The magnifier is set with view for a cylinder or buret and with beakerView for a beaker (off by default, since beaker marks are coarse).

### Examples

- [A 50 mL buret reading 23.47 mL, with a magnifier and the answer key.](https://chemistryfigures.com/volume-reading?instrument=buret&reading=23.47&answerKey=1)
- [A 10 mL graduated cylinder reading 6.54 mL, with no magnifier.](https://chemistryfigures.com/volume-reading?size=10&reading=6.54&view=whole)
- [A 250 mL (medium) beaker of blue liquid at 175 mL, titled “Read the volume”.](https://chemistryfigures.com/volume-reading?instrument=beaker&reading=175&tint=blue&titleMode=text&title=Read+the+volume)

## Volume by Displacement

https://chemistryfigures.com/volume-by-displacement

Make printable water displacement figures for chemistry tests. Type the before and after readings and get two graduated cylinders, with an object in the second, for students to find its volume.

Two graduated cylinders side by side: before, with water at the before reading, and after, with the object in and water at the after reading. The object’s volume is after minus before.

### Parameters

- size (choice: 10, 25, 50, 100; default 10): Both cylinders’ capacity, in mL.
- before (number: 0 to 100; default 4): The water level before the object goes in, in mL.
- after (number: 0 to 100. Always above before; default 6): The water level with the object in, in mL.
- tint (choice: gray, blue, red, green; default gray): The water’s color. Gray photocopies best.
- object (choice: marbles, rock, cube, cylinder. marbles: marbles; rock: rock; cube: cube; cylinder: metal cylinder; default marbles): The object dropped into the second cylinder.
- marbles (number: 1 to 5; default 2; used when object=marbles): How many marbles. Rounded to a whole number.
- view (choice: whole, both. whole: cylinders only; both: cylinders and magnifiers; default whole): Whether a magnified circle of the scale is drawn beside each cylinder.
- span (number: 1 to 6; default 3; used when view=both): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- beforeCaption (text: up to 40 characters; default Before): The caption under the first cylinder.
- afterCaption (text: up to 40 characters; default After): The caption under the second cylinder.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “Before: 4.00 mL · After: 6.00 mL · Object: 2.00 mL”.

### Rules between parameters

- before and after are in mL, rounded to the cylinder’s estimated digit (10 mL to 2 decimal places, 25 mL to 2 decimal places, 50 mL to 1 decimal place, 100 mL to 1 decimal place) and kept within its capacity.
- after is always higher than before: an after reading that isn’t is raised to one step above before.
- marbles sets how many marbles only when object=marbles.

### Examples

- [A rock raising the water in a 100 mL cylinder from 52.0 to 67.5 mL (a 15.5 mL rock), with the answer key.](https://chemistryfigures.com/volume-by-displacement?size=100&before=52&after=67.5&object=rock&answerKey=1)
- [Three marbles in a 25 mL cylinder, 12.50 to 15.75 mL, with magnifiers.](https://chemistryfigures.com/volume-by-displacement?size=25&before=12.5&after=15.75&marbles=3&view=both)
- [A metal cylinder in a 50 mL cylinder, 20.0 to 27.0 mL, captioned “Initial” and “Final”.](https://chemistryfigures.com/volume-by-displacement?size=50&before=20&after=27&object=cylinder&beforeCaption=Initial&afterCaption=Final)

## Gas Syringe

https://chemistryfigures.com/gas-syringe

Make printable gas syringe figures for chemistry tests. Type a volume of gas in cm³ or mL and students read it from the plunger of a 50 or 100 cm³ syringe, alone or set up with a conical flask and stand, with a magnified view for the estimated digit.

A glass gas syringe lying on its side, marked every 1 and numbered every 10 from 0 at the nozzle, with the plunger pushed out to the volume of gas in reading. It can be drawn alone or collecting gas from a conical flask on a stand.

### Parameters

- size (choice: 50, 100; default 100): The syringe’s capacity (50 or 100 cm³). Both are drawn the same length; the 50 is thinner.
- unit (choice: cm3, mL. cm3: cm³; mL: mL; default cm3): The unit printed on the scale and in the answer key.
- reading (number: 0 to 100. Rounded to 1 decimal place, 0 up to size; default 43.6): The volume of gas collected, read at the plunger’s face.
- setup (choice: syringe, setup. syringe: syringe only; setup: with a conical flask, delivery tube and stand; default setup): Whether the syringe is drawn alone or set up to collect gas.
- view (choice: both, magnifier, whole. both: the instrument with a magnified circle of its scale beside it; magnifier: the magnified circle alone; whole: the instrument alone; default both): What the figure shows. The magnifier sits above the syringe.
- span (number: 1 to 6; default 2; used when view=both or view=magnifier): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “Volume of gas: 43.6 cm³”.

### Rules between parameters

- reading is rounded to 1 decimal place and kept between 0 and the syringe’s size (50 or 100).
- unit only changes what the scale is labeled: 1 cm³ = 1 mL, so it never changes the reading.

### Examples

- [A 100 cm³ gas syringe alone, holding 62.4 cm³ of gas, with no magnifier.](https://chemistryfigures.com/gas-syringe?reading=62.4&setup=syringe&view=whole)
- [A 50 mL gas syringe collecting gas from a flask, reading 18.5 mL, with a magnifier and the answer key.](https://chemistryfigures.com/gas-syringe?size=50&unit=mL&reading=18.5&answerKey=1)

## Length Reading

https://chemistryfigures.com/length-reading

Make printable ruler figures for chemistry tests. Pick a centimeter or inch ruler and how finely it is marked, type an object’s length, and students measure it, lined up with 0 or starting partway along, with magnified views of its ends.

A metric (cm) or imperial (inch) ruler with an object lying along its top edge. length is the object’s length and start is where its left end sits, both in the ruler’s unit; start=0 lines it up with the 0 mark.

### Parameters

- system (choice: metric, imperial. metric: centimeters; imperial: inches; default metric): Which kind of ruler.
- cm (choice: 15, 20, 30, 50, 100; default 15; used when system=metric): The metric ruler’s length in cm (100 is a meter stick).
- inches (choice: 6, 8, 12, 20; default 6; used when system=imperial): The imperial ruler’s length in inches.
- metricMarks (choice: ten, five, cm, half, mm. ten: 10 cm; five: 5 cm; cm: 1 cm; half: 0.5 cm; mm: 1 mm; default mm; used when system=metric): The metric ruler’s smallest marks.
- imperialMarks (choice: 1, 2, 4, 8, 16; default 8; used when system=imperial): Marks per inch on the imperial ruler (16 is sixteenths).
- read (choice: estimate, mark. estimate: one estimated digit; mark: nearest mark; default estimate; used when system=metric): How far a metric reading goes.
- object (choice: marbles, rock, cube, cylinder. marbles: marbles; rock: rock; cube: cube; cylinder: metal cylinder; default cylinder): The object lying along the ruler.
- marbles (number: 1 to 5; default 3; used when object=marbles): How many marbles, in a row. Rounded to a whole number.
- guides (on/off: 1 (on) or 0 (off); default 0): Dashed lines from the object’s ends down to the ruler, for round objects whose ends are above where they touch it.
- length (number: 0 to 100. Rounded to what the ruler reads (see notes); default 4.37): The object’s length, in cm or inches.
- start (number: 0 to 100; default 0): Where the object’s left end sits on the ruler, in cm or inches; 0 lines it up with the 0 mark.
- view (choice: both, whole. both: ruler and magnifiers; whole: ruler only; default both): Whether magnified circles are drawn at the object’s ends: one on its right end, and one on its left end when that isn’t at 0.
- span (number: 1 to 6; default 3; used when view=both): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “Length: 4.37 cm”.

### Rules between parameters

- cm, metricMarks and read apply only when system=metric; inches and imperialMarks only when system=imperial.
- 5 cm and 10 cm marks (metricMarks=five or ten) are only for the 50 and 100 cm rulers; on a shorter ruler they become 1 cm marks.
- length and start are rounded to what the ruler reads: with read=estimate, one digit past the smallest mark (1 mm marks to 0.01 cm; 1 cm and 0.5 cm marks to 0.1 cm; 5 and 10 cm marks to 1 cm); with read=mark, to the nearest mark. Imperial lengths always land on a mark: write them as decimals (3.375 for 3 3/8 in).
- length is at least 0.5 cm (or 0.25 in, or one reading step if bigger) and start is kept so the object stays on the ruler.

### Examples

- [A metal cylinder 6.42 cm long on a 15 cm ruler marked in mm, starting at 0, with the answer key.](https://chemistryfigures.com/length-reading?length=6.42&answerKey=1)
- [A rock from 2.3 cm to 8.1 cm on a 30 cm ruler marked every 1 cm, so students subtract the ends.](https://chemistryfigures.com/length-reading?cm=30&metricMarks=cm&object=rock&guides=1&length=5.8&start=2.3)
- [A cube 2 3/8 in long on a 6 in ruler marked in eighths, with no magnifiers.](https://chemistryfigures.com/length-reading?system=imperial&object=cube&length=2.375&view=whole)

## Mass Reading

https://chemistryfigures.com/mass-reading

Make printable balance figures for chemistry tests. Type a mass and get a digital, analytical or triple beam balance showing it, for students to read.

A triple beam balance (610 g, read to 2 decimal places from its three riders) or a digital balance whose display shows mass in grams.

### Parameters

- instrument (choice: triple-beam, digital. triple-beam: triple beam balance; digital: digital balance; default triple-beam): Which balance.
- decimals (number: 1 to 4; default 2; used when instrument=digital): How many decimal places of grams the digital display shows. Rounded to a whole number.
- pan (choice: boat, beaker, empty. boat: a weigh boat; beaker: a beaker; empty: nothing; default boat; used when instrument=digital and object=none): What the digital balance’s pan holds.
- object (choice: none, marbles, rock, cube, cylinder. none: no object; marbles: marbles; rock: rock; cube: cube; cylinder: metal cylinder; default none): An object on the pan, drawn as in Volume by Displacement.
- marbles (number: 1 to 5; default 2; used when object=marbles): How many marbles. Rounded to a whole number.
- mass (number: 0 to 1000. Rounded and kept within the balance’s capacity (see notes); default 24.73): The mass shown, in grams.
- view (choice: both, whole, beams. both: the balance with a magnifier on the 0–10 g beam’s rider; whole: the balance alone; beams: just the beams and riders; default both; used when instrument=triple-beam): What a triple beam figure shows.
- span (number: 1 to 6; default 3; used when instrument=triple-beam and view=both): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “Mass: 24.73 g”.

### Rules between parameters

- mass is in grams, rounded to the balance’s decimal places and kept between 0 and its capacity: triple beam 610 g to 2 places; digital 1 place: up to 1000 g; 2 places: up to 400 g; 3 places: up to 200 g, an analytical balance in a draft shield; 4 places: up to 200 g, an analytical balance in a draft shield.
- decimals and pan apply only to the digital balance; view and span only to the triple beam balance.
- An object other than none sits on either balance’s pan, in place of the digital balance’s pan contents.

### Examples

- [A triple beam balance reading 347.85 g, with a magnifier on the front rider and the answer key.](https://chemistryfigures.com/mass-reading?mass=347.85&answerKey=1)
- [A digital balance showing 12.6 g with a rock on its pan.](https://chemistryfigures.com/mass-reading?instrument=digital&decimals=1&object=rock&mass=12.6)
- [An analytical balance (4 decimal places) showing 0.2534 g in a weigh boat.](https://chemistryfigures.com/mass-reading?instrument=digital&decimals=4&mass=0.2534)

## Temperature Reading

https://chemistryfigures.com/temperature-reading

Make printable thermometer figures for chemistry tests. Type a temperature in Celsius, Kelvin or Fahrenheit and students read it from a liquid-in-glass thermometer, with a magnified view for the estimated digit, or from a digital probe thermometer.

A liquid-in-glass thermometer (read at the top of its liquid column, with an optional magnifier) or a digital probe thermometer standing in a beaker, showing reading in the chosen unit.

### Parameters

- instrument (choice: glass, digital. glass: liquid-in-glass thermometer; digital: digital probe thermometer; default glass): Which thermometer.
- unit (choice: celsius, kelvin, fahrenheit. celsius: °C; kelvin: K; fahrenheit: °F; default celsius): The temperature scale the thermometer reads in.
- decimals (number: 0 to 2; default 1; used when instrument=digital): Decimal places on the digital display. Rounded to a whole number.
- reading (number: -100 to 500. Rounded and kept within the thermometer’s range (see notes); default 23.4): The temperature shown, in the chosen unit.
- tint (choice: red, blue, gray; default red; used when instrument=glass): The glass thermometer’s liquid color (red like alcohol, gray like mercury).
- view (choice: both, magnifier, whole. both: the instrument with a magnified circle of its scale beside it; magnifier: the magnified circle alone; whole: the instrument alone; default both; used when instrument=glass): What a glass thermometer figure shows.
- span (number: 1 to 6; default 3; used when instrument=glass and view is both or magnifier): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “Temperature: 23.4 °C”.

### Rules between parameters

- reading is in the unit set by unit: unit=kelvin&reading=300 is 300 K. Give reading whenever you change unit, since the default 23.4 is outside the Kelvin glass scale and would be clamped to its bottom.
- On the glass thermometer reading is rounded to 1 decimal place and kept on the scale: -10 to 110 °C marked every 1, 260 to 390 K marked every 1, 10 to 230 °F marked every 2.
- On the digital thermometer reading is rounded to decimals places and kept within -50 to 150 °C, 223 to 423 K, -58 to 302 °F.
- decimals applies only to the digital thermometer; tint, view and span only to the glass one.

### Examples

- [A liquid-in-glass thermometer reading 78.5 °C, with a magnifier and the answer key.](https://chemistryfigures.com/temperature-reading?reading=78.5&answerKey=1)
- [A digital thermometer showing −12.35 °C.](https://chemistryfigures.com/temperature-reading?instrument=digital&decimals=2&reading=-12.35)
- [A liquid-in-glass thermometer marked in kelvins, reading 310.0 K, with a gray (mercury) column and no magnifier.](https://chemistryfigures.com/temperature-reading?unit=kelvin&reading=310&tint=gray&view=whole)

## pH Reading

https://chemistryfigures.com/ph-reading

Make printable pH meter figures for chemistry tests. Type a pH and students read it from a digital pH meter, from an analog meter with a magnified view for the estimated digit, or by matching a strip of pH paper to its color chart.

A pH meter wired to an electrode in a beaker, digital or analog (a needle over a 0–14 dial), or a strip of universal indicator paper above its color chart, showing the pH in reading.

### Parameters

- instrument (choice: digital, analog, paper. digital: digital pH meter; analog: analog pH meter; paper: pH paper and color chart; default digital): Which instrument.
- decimals (number: 1 to 2; default 2; used when instrument=digital): Decimal places on the digital display. Rounded to a whole number.
- reading (number: 0 to 14. Rounded to what the instrument reads (see notes); default 4.62): The pH shown.
- view (choice: both, magnifier, whole. both: the instrument with a magnified circle of its scale beside it; magnifier: the magnified circle alone; whole: the instrument alone; default both; used when instrument=analog): What an analog meter figure shows.
- span (number: 1 to 6; default 3; used when instrument=analog and view is both or magnifier): How many numbered marks the magnified circle spans; fewer marks means a bigger zoom. Rounded to a whole number.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “pH: 4.62”.

### Rules between parameters

- reading is kept between 0 and 14 and rounded to what the instrument reads: the digital meter to decimals places, the analog meter to 2 places (marks every 0.2), and pH paper to the whole number whose color it matches.
- decimals applies only to the digital meter; view and span only to the analog meter.
- pH paper only works printed in color.

### Examples

- [A digital pH meter showing 8.34, with the answer key.](https://chemistryfigures.com/ph-reading?reading=8.34&answerKey=1)
- [An analog pH meter at pH 3.46, with a magnifier on the needle.](https://chemistryfigures.com/ph-reading?instrument=analog&reading=3.46)
- [pH paper that has turned the color for pH 11, above the 0–14 color chart.](https://chemistryfigures.com/ph-reading?instrument=paper&reading=11)

## Titration Curve

https://chemistryfigures.com/titration-curve

Make printable titration curves for chemistry tests. Pick a strong or weak acid or base, type the molarities, volume and pKa, or just the starting, equivalence and ending pH, and get the curve with its equivalence and half-equivalence points marked.

A graph of pH (up the side) against the volume of titrant added in mL (along the bottom) for one monoprotic acid titrated with NaOH or base titrated with HCl. The curve is worked out either from concentrations (source=chemistry) or from key points (source=points).

### Parameters

- source (choice: chemistry, points. chemistry: concentrations; points: key points; default chemistry): What the curve is worked out from.
- analyte (choice: strong-acid, weak-acid, strong-base, weak-base. strong-acid: strong acid with a strong base; weak-acid: weak acid with a strong base; strong-base: strong base with a strong acid; weak-base: weak base with a strong acid; default weak-acid): What is in the flask. An acid is titrated with NaOH, a base with HCl.
- analyteM (number: 0.0001 to 10; default 0.1; used when source=chemistry): The acid or base’s molarity, in M.
- analyteMl (number: 0.1 to 1000; default 25; used when source=chemistry): The volume of acid or base in the flask, in mL.
- titrantM (number: 0.0001 to 10; default 0.1; used when source=chemistry): The NaOH or HCl molarity, in M.
- pKa (number: 0 to 14; default 4.76; used when source=chemistry and analyte=weak-acid): The weak acid’s pKa.
- pKb (number: 0 to 14; default 4.75; used when source=chemistry and analyte=weak-base): The weak base’s pKb.
- startPH (number: 0 to 14; default 2.88; used when source=points): The pH before any titrant is added.
- eqMl (number: 0.01 to 1000; default 25; used when source=points): The volume of titrant at the equivalence point, in mL.
- eqPH (number: 0 to 14; default 8.73; used when source=points): The pH at the equivalence point.
- endPH (number: 0 to 14; default 12.52; used when source=points): The pH at the end of the x-axis.
- eqMark (choice: guides, dot, none. guides: dot and lines to the axes; dot: dot; none: not marked; default guides): How the equivalence point is marked.
- eqLabelMode (choice: text, blank, none. text: the words given; blank: a blank line for students to write on; none: nothing; default text; used when eqMark is not none): The equivalence point’s label.
- eqLabel (text: up to 120 characters; default Equivalence point; used when eqLabelMode=text): The equivalence point label’s words.
- halfMark (choice: guides, dot, none. guides: dot and lines to the axes; dot: dot; none: not marked; default none; used when analyte is weak-acid or weak-base): How the half-equivalence point is marked.
- halfLabelMode (choice: text, blank, none. text: the words given; blank: a blank line for students to write on; none: nothing; default text; used when halfMark is not none): The half-equivalence point’s label.
- halfLabel (text: up to 120 characters; default Half-equivalence point; used when halfLabelMode=text): The half-equivalence point label’s words.
- color (choice: black, blue, red, green, orange, purple; default blue): The curve’s color.
- xFrom (text: up to 120 characters; default 0): The x-axis’s start, in mL, written as a plain number (e.g. 0, 2.5).
- xTo (text: up to 120 characters; default 50): The x-axis’s end, in mL; the curve runs to here, written as a plain number (e.g. 0, 2.5).
- xStep (text: up to 120 characters; default 2): The x-axis’s gridline spacing, in mL, written as a plain number (e.g. 0, 2.5).
- yFrom (text: up to 120 characters; default 0): The y-axis’s start, in pH, written as a plain number (e.g. 0, 2.5).
- yTo (text: up to 120 characters; default 14): The y-axis’s end, in pH, written as a plain number (e.g. 0, 2.5).
- yStep (text: up to 120 characters; default 1): The y-axis’s gridline spacing, in pH, written as a plain number (e.g. 0, 2.5).
- xEvery (choice: 1, 2, 5, 10, 0; default 5): Number every nth x gridline; 0 leaves the x-axis unnumbered.
- yEvery (choice: 1, 2, 5, 10, 0; default 2): Number every nth y gridline; 0 leaves the y-axis unnumbered.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- titleMode (choice: text, blank, none. text: the words given; blank: a blank line for students to write on; none: nothing; default none): The chart title across the top.
- xTitle (text: up to 120 characters; default Volume of NaOH added (mL); used when xTitleMode=text): The x-axis title’s words.
- xTitleMode (choice: text, blank, none. text: the words given; blank: a blank line for students to write on; none: nothing; default text): The x-axis title.
- yTitle (text: up to 120 characters; default pH; used when yTitleMode=text): The y-axis title’s words.
- yTitleMode (choice: text, blank, none. text: the words given; blank: a blank line for students to write on; none: nothing; default text): The y-axis title.
- xLabel (text: up to 120 characters; default x; used when xLabelMode=text): The letter at the end of the x-axis.
- xLabelMode (choice: text, none; default none): Whether the x-axis has a letter at its end.
- yLabel (text: up to 120 characters; default y; used when yLabelMode=text): The letter at the end of the y-axis.
- yLabelMode (choice: text, none; default none): Whether the y-axis has a letter at its end.
- xStartCap (choice: triangle, line, circle, none; default none): How the x-axis’s left end is finished.
- xEndCap (choice: triangle, line, circle, none; default none): How the x-axis’s right end is finished.
- yStartCap (choice: triangle, line, circle, none; default none): How the y-axis’s bottom end is finished.
- yEndCap (choice: triangle, line, circle, none; default none): How the y-axis’s top end is finished.
- minor (choice: 0, 2, 4, 5; default 0): Minor gridlines: how many parts each grid block is split into; 0 for none.
- labelSize (choice: small, medium, large; default medium): How big the figure’s text is compared to its lines.

### Rules between parameters

- With source=chemistry (the default) the curve comes from analyteM, analyteMl, titrantM and pKa (weak acid) or pKb (weak base); the pH at each volume is solved exactly. startPH, eqMl, eqPH and endPH are ignored.
- With source=points the curve is a real titration curve bent to pass through startPH, the equivalence point (eqMl, eqPH) and endPH, which is the pH at the end of the x-axis. The concentrations are ignored.
- The defaults are 25.0 mL of 0.100 M acetic acid (pKa 4.76) titrated with 0.100 M NaOH. The page’s common titrations are all 25.0 mL of 0.100 M with 0.100 M: HCl with NaOH: analyte=strong-acid; CH₃COOH (acetic acid) with NaOH: analyte=weak-acid, pKa=4.76; HCOOH (formic acid) with NaOH: analyte=weak-acid, pKa=3.75; HF with NaOH: analyte=weak-acid, pKa=3.17; NaOH with HCl: analyte=strong-base; NH₃ (ammonia) with HCl: analyte=weak-base, pKb=4.75.
- The x-axis title is not changed by the link: for a base (analyte=strong-base or weak-base) also set xTitle, e.g. “Volume of HCl added (mL)”.
- The half-equivalence point (halfMark and its label) is drawn only for a weak acid or weak base.
- Axis ranges are text holding plain numbers. From xFrom to xTo counting by xStep makes the gridlines, at most 50 blocks per axis; an axis whose range can’t be used falls back to 0 to 15 by 1.

### Examples

- [Acetic acid (25.0 mL, 0.100 M, pKa 4.76) titrated with 0.100 M NaOH, with the equivalence and half-equivalence points marked.](https://chemistryfigures.com/titration-curve?halfMark=guides)
- [Ammonia (0.100 M, pKb 4.75) titrated with 0.100 M HCl, the half-equivalence point marked with a dot.](https://chemistryfigures.com/titration-curve?analyte=weak-base&halfMark=dot&xTitle=Volume+of+HCl+added+%28mL%29)
- [A strong acid curve from key points (starting pH 1, equivalence at 20 mL and pH 7, ending pH 12.5), its equivalence label left blank for students.](https://chemistryfigures.com/titration-curve?source=points&analyte=strong-acid&startPH=1&eqMl=20&eqPH=7&endPH=12.5&eqLabelMode=blank)

## Particle Diagram

https://chemistryfigures.com/particle-diagram

Make printable particle diagrams for AP Chemistry tests. Pick the atoms, ions and molecules, their sizes, shades and charges, and how many of each, and get them scattered in a box or packed in an ionic or alloy lattice, with a key.

Atoms, ions and molecules drawn as plain discs, either scattered at random in a fixed square box (layout=scattered, from the particles list) or packed in a lattice (layout=lattice, from main and second). An optional key beside the box names each kind.

### Parameters

- layout (choice: scattered, lattice. scattered: at random in a box, for a gas, liquid or solution; lattice: packed in a grid, for a solid; default scattered): How the particles are arranged.
- particles (JSON: JSON, URL-encoded; default [{"count":4,"shape":"single","look":{"size":"l","shade":"light","charge":"-"},"outer":{"size":"s","shade":"white","charge":""}},{"count":4,"shape":"single","look":{"size":"s","shade":"white","charge":"+"},"outer":{"size":"s","shade":"white","charge":""}}]; used when layout=scattered): The particle kinds scattered in the box, as JSON (see notes).
- seed (number: 1 to 999999; default 2): Which random arrangement is drawn. Rounded to a whole number.
- border (choice: single, double, none; default single; used when layout=scattered): The scattered box’s border.
- pattern (choice: pure, alternate, substitute, interstitial. pure: one kind (a pure metal); alternate: alternating (an ionic solid); substitute: substitutional alloy; interstitial: interstitial alloy; default alternate; used when layout=lattice): The lattice’s pattern.
- rows (number: 1 to 12; default 4; used when layout=lattice): The lattice’s rows. Rounded to a whole number.
- columns (number: 1 to 12; default 5; used when layout=lattice): The lattice’s columns. Rounded to a whole number.
- spacing (choice: touching, spaced; default touching; used when layout=lattice): Whether the lattice’s atoms or ions touch or are evenly spaced apart.
- main (JSON: JSON, URL-encoded; default {"size":"l","shade":"light","charge":"-"}; used when layout=lattice): The lattice’s main atom or ion, as JSON: {"size":…,"shade":…,"charge":…}.
- second (JSON: JSON, URL-encoded; default {"size":"s","shade":"white","charge":"+"}; used when layout=lattice and pattern is not pure): The lattice’s second atom or ion, as JSON like main.
- secondCount (number: 0 to 144; default 4; used when pattern is substitute or interstitial): How many second atoms a substitutional or interstitial lattice has, up to its room (see notes). Rounded to a whole number.
- mainName (text: up to 40 characters; default (empty); used when layout=lattice): The key’s name for the lattice’s main kind.
- secondName (text: up to 40 characters; default (empty); used when layout=lattice and pattern is not pure): The key’s name for the lattice’s second kind.
- latticeBorder (choice: single, double, none; default none; used when layout=lattice): The border around a lattice.
- show (choice: box, both, key. box: the box only; both: the box and its key; key: the key only (so separate answer choices can share one key); default box): What the figure shows.
- keyNote (text: up to 80 characters; default (empty); used when show is both or key): A note line at the bottom of the key, e.g. “H₂O molecules are not shown”.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.

### Rules between parameters

- particles is a URL-encoded JSON array of 1 to 4 particle kinds, each {"count":0–60,"shape":…,"look":LOOK,"outer":LOOK,"name":"…"}. shape is one of single (alone), pair (pair), bent (bent), line (in a line), triangle (three around), cross (four around); look is the center (or only) disc and outer every disc around it. A look is {"size":…,"shade":…,"charge":…}, where size is xs, s, m, l, xl; shade is white (white), light (light gray), gray (gray), dark (dark gray), black (black); and charge is "" (none, an atom), +, -, 2+, 2-, 3+, 3-. A missing count is 1, a missing look is medium white with no charge, a missing outer is small white with no charge, and name (up to 40 characters) is what the key calls the kind. A kind with count 0 appears only in the key. Particles that don’t fit in the box are left out.
- seed picks the random positions (and, in a lattice, which sites get the second kind); the same seed always gives the same figure.
- In a lattice, pattern=pure uses main only; alternate alternates main and second like an ionic solid; substitute swaps secondCount sites for second (room for rows × columns); interstitial puts secondCount second atoms in the gaps between four (room for (rows − 1) × (columns − 1), e.g. 12 in a 4 × 5 lattice).
- border applies to the scattered box and latticeBorder to the lattice (none by default).

### Examples

- [A gas mixture: 5 diatomic molecules of dark gray atoms and 4 large white atoms, scattered in a box with a key naming them.](https://chemistryfigures.com/particle-diagram?particles=%5B%7B%22count%22%3A5%2C%22shape%22%3A%22pair%22%2C%22look%22%3A%7B%22size%22%3A%22m%22%2C%22shade%22%3A%22dark%22%2C%22charge%22%3A%22%22%7D%2C%22outer%22%3A%7B%22size%22%3A%22m%22%2C%22shade%22%3A%22dark%22%2C%22charge%22%3A%22%22%7D%2C%22name%22%3A%22Cl%E2%82%82+molecule%22%7D%2C%7B%22count%22%3A4%2C%22shape%22%3A%22single%22%2C%22look%22%3A%7B%22size%22%3A%22l%22%2C%22shade%22%3A%22white%22%2C%22charge%22%3A%22%22%7D%2C%22outer%22%3A%7B%22size%22%3A%22s%22%2C%22shade%22%3A%22white%22%2C%22charge%22%3A%22%22%7D%2C%22name%22%3A%22Ar+atom%22%7D%5D&show=both)
- [An ionic solid: a 4 × 4 alternating lattice of large − ions and small + ions, with a key naming them Cl⁻ and Na⁺.](https://chemistryfigures.com/particle-diagram?layout=lattice&columns=4&mainName=Cl%E2%81%BB+ion&secondName=Na%E2%81%BA+ion&show=both)
- [An interstitial alloy: a 5 × 6 lattice of gray atoms with 6 tiny black atoms in the gaps, and a key.](https://chemistryfigures.com/particle-diagram?layout=lattice&pattern=interstitial&rows=5&columns=6&main=%7B%22size%22%3A%22l%22%2C%22shade%22%3A%22gray%22%2C%22charge%22%3A%22%22%7D&second=%7B%22size%22%3A%22xs%22%2C%22shade%22%3A%22black%22%2C%22charge%22%3A%22%22%7D&secondCount=6&mainName=Fe+atom&secondName=C+atom&show=both)

## Bohr Model

https://chemistryfigures.com/bohr-model

Make printable Bohr model diagrams for chemistry tests. Pick any element and charge, or set the protons, neutrons and electrons on each shell, and get the nucleus and rings in your colors, with an ion’s gained and lost electrons marked, empty rings or a blank nucleus for students to complete.

One atom or ion: a nucleus of protons and neutrons with electrons as dots on rings. The link gives the counts themselves (protons, neutrons, and electrons on each shell); there is no element parameter, and nothing is checked, so any counts draw exactly as given.

### Parameters

- protons (number: 0 to 200. Up to 200; default 6): The number of protons. Rounded to a whole number.
- neutrons (number: 0 to 200. Up to 200; default 6): The number of neutrons. Rounded to a whole number.
- nucleus (choice: balls, text, blank. balls: proton and neutron balls; text: the counts written in a circle; blank: an empty circle for students; default balls): How the nucleus is drawn.
- seed (number: 1 to 999999; default 1; used when nucleus=balls): Which random mix of proton and neutron balls is drawn. Rounded to a whole number.
- electrons (text: whole numbers joined by hyphens, e.g. 2-8-1 (1 to 7 shells, each 0 to 32); default 2-4): The electrons on each shell, innermost first.
- placement (choice: even, paired. even: spread evenly; paired: the first four singly at top, right, bottom and left, then in pairs, as in Lewis structures (up to 8 per shell; fuller shells are spread evenly); default even): How electrons sit on each ring.
- emptyRings (on/off: 1 (on) or 0 (off); default 0): Draws the rings without electrons, for students to draw them.
- protonColor (choice: red, orange, yellow, green, blue, purple, gray, white, black; default red; used when nucleus=balls): The proton balls’ color.
- protonSymbol (choice: +, p, p+, (empty). p+ is written p⁺; empty for none; default +): The symbol written on each proton ball or dot, or none.
- neutronColor (choice: red, orange, yellow, green, blue, purple, gray, white, black; default gray; used when nucleus=balls): The neutron balls’ color.
- neutronSymbol (choice: 0, n, n0, (empty). n0 is written n⁰; empty for none; default (empty)): The symbol written on each neutron ball or dot, or none.
- electronColor (choice: red, orange, yellow, green, blue, purple, gray, white, black; default blue): The electron dots’ color.
- electronSymbol (choice: -, e, e-, (empty). e- is written e⁻; empty for none. An electron with a symbol is drawn larger; default (empty)): The symbol written on each electron ball or dot, or none.
- gainedLost (on/off: 1 (on) or 0 (off); default 0): Shows gained and lost electrons compared with the neutral atom (see notes).
- gainedColor (choice: red, orange, yellow, green, blue, purple, gray, white, black; default green; used when gainedLost=1): The gained electrons’ color.
- brackets (on/off: 1 (on) or 0 (off); default 0): Puts an ion in square brackets with its charge at the top right.
- key (on/off: 1 (on) or 0 (off); default 0): Draws a key beside the model naming each part drawn as a ball or dot.
- shellLabels (on/off: 1 (on) or 0 (off); default 0): Writes n = 1, n = 2… on each ring.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.

### Rules between parameters

- electrons lists each shell’s electrons from the nucleus out, joined by hyphens: 2-8-1 is sodium’s. 1 to 7 shells, each 0 to 32.
- To draw an element, set protons to its atomic number, neutrons to its mass number minus that, and electrons to its shells (the page uses the atomic mass rounded to a whole number; Cl is 17 protons, 18 neutrons, 2-8-7). For an ion, change only electrons: Na⁺ is protons=11&neutrons=12&electrons=2-8.
- The charge (protons minus electrons) is worked out, never given. brackets draws square brackets and the charge around an ion; a neutral atom is never bracketed.
- nucleus=balls draws proton and neutron balls only up to 40 of them combined; past that it shows the counts as text.
- gainedLost shows how the shells differ from the neutral atom’s (gained electrons in gainedColor, lost ones as dashed empty spots) only when protons is an element’s atomic number and emptyRings is off.

### Examples

- [A sodium atom: 11 protons and 12 neutrons as balls, electrons 2, 8, 1, with shell labels and a key.](https://chemistryfigures.com/bohr-model?protons=11&neutrons=12&electrons=2-8-1&key=1&shellLabels=1)
- [A chloride ion, Cl⁻ (2, 8, 8), in brackets, with its gained electron in green.](https://chemistryfigures.com/bohr-model?protons=17&neutrons=18&electrons=2-8-8&gainedLost=1&brackets=1)
- [An oxygen atom with its nucleus written as text and its rings left empty for students to draw the electrons.](https://chemistryfigures.com/bohr-model?protons=8&neutrons=8&nucleus=text&electrons=2-6&emptyRings=1)

## Lewis Structures

https://chemistryfigures.com/lewis-structures

Make printable Lewis structures for chemistry tests. Type a formula like H2O or SO4 2- and get its Lewis dot structure, with formal charges and resonance structures, a structure for students to complete, or a wrong one for students to find the mistakes in.

The Lewis structure of one molecule or polyatomic ion, from formula. It always starts correct; scaffold turns it into a “complete this” question, and central or changes turn it into a “find the mistake” question.

### Parameters

- formula (text: up to 40 characters. Up to 40 characters; default H2O): The molecule or ion, as a formula or a listed name (see notes).
- which (text: up to 40 characters. A listed id, e.g. ethanol or dimethyl-ether; default (empty)): Which listed structure, by id, when several share the formula’s atoms.
- rule (choice: octet, fewest. octet: the octet rule; fewest: fewest formal charges; default octet): The structure rule.
- resonance (choice: one, all; default one): For a molecule or ion with resonance structures, whether to draw one of them or all of them in a row joined by ↔.
- form (number: 1 to 99; default 1; used when resonance=one): Which resonance structure to draw, counting from 1. Rounded to a whole number; past the last one draws the last.
- shape (choice: flat, shaped. flat: outer atoms on the four sides, as in most textbooks; shaped: hinting at the real shape (bent H₂O); default flat): How the atoms are placed.
- bondStyle (choice: lines, dots. lines: a line per shared pair; dots: two dots per shared pair; default lines): How bonds are drawn.
- formalCharges (on/off: 1 (on) or 0 (off); default 0): Labels atoms with their formal charges.
- scaffold (choice: full, bonds, skeleton. full: the whole structure; bonds: bonds without lone electrons; skeleton: just the atoms placed; default full): How much of the structure a “complete this” question gives.
- central (text: up to 2 characters. An element symbol in the formula, e.g. O in CO2; ignored for listed structures and formulas under 3 atoms; default (empty)): Rebuilds a structure made from its formula around another of its elements as the central atom, making a “find the mistake” question.
- changes (text: items joined by dots: bN_O sets bond N to order O (0–3); lN_E gives atom N E lone electrons (0–8); fN_C labels atom N with formal charge C; k_1 or k_0 turns brackets on or off; q_C writes the ion’s charge as C. A negative number is written with m, e.g. f2_m1; default (empty)): Edits to the correct structure, for a “find the mistake” question. Atoms and bonds are numbered from 0 in the structure’s own order, so these are easiest made on the page and copied with Share link.
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0; used when scaffold is not full, or the structure is changed): Prints the answer key under the figure: the full structure under a scaffolded one, the list of mistakes under a changed one.

### Rules between parameters

- formula is a formula such as H2O, CH4, NH4+, SO4 2- or SO4^2- (a charge of 2 or more needs a space, ^ or parentheses before it: SO42- would be 42 oxygens), or pasted with real subscripts (SO₄²⁻). URL-encode it: a space is + or %20 and a plus sign is %2B, so NH4+ is formula=NH4%2B and SO4 2- is formula=SO4+2-.
- Molecules with more than one central atom come from a list and can also be given by name: ethane (C2H6), ethene (C2H4), ethyne (C2H2), methanol (CH3OH), ethanol (C2H5OH), dimethyl ether (CH3OCH3), acetic acid (CH3COOH), acetate (CH3COO-), formic acid (HCOOH), methylamine (CH3NH2), hydrazine (N2H4), hydrogen peroxide (H2O2), nitrous oxide (N2O), hypochlorous acid (HOCl), nitrous acid (HNO2), nitric acid (HNO3), carbonic acid (H2CO3), hydrogen carbonate (HCO3-), sulfuric acid (H2SO4), phosphoric acid (H3PO4), perchloric acid (HClO4).
- When a formula matches more than one listed structure by its atoms, which picks one by id: ethanol, dimethyl-ether.
- rule decides which correct structure is built where textbooks disagree (SO₄²⁻, PO₄³⁻, ClO₄⁻, SO₂, SO₃): octet gives every atom an octet with formal charges; fewest lets period 3 and lower atoms exceed eight electrons for the fewest formal charges.
- A figure is either a “complete this” question or a “find the mistake” question: when central or changes change the structure, it is drawn in full as one structure, whatever scaffold and resonance say.
- answerKey prints, under a scaffolded structure, the full structure, and under a changed one, a list of its mistakes. A correct full structure has no answer key.

### Examples

- [Sulfate, SO₄²⁻, under the octet rule, in brackets, with formal charges.](https://chemistryfigures.com/lewis-structures?formula=SO4+2-&formalCharges=1)
- [All three resonance structures of nitrate, NO₃⁻, joined by ↔.](https://chemistryfigures.com/lewis-structures?formula=NO3-&resonance=all)
- [The skeleton of ammonia, NH₃, shaped, for students to complete, with the full structure as the answer key.](https://chemistryfigures.com/lewis-structures?formula=NH3&shape=shaped&scaffold=skeleton&answerKey=1)
- [Carbon dioxide wrongly built around an O atom, for students to find the mistake, which the answer key names.](https://chemistryfigures.com/lewis-structures?formula=CO2&central=O&answerKey=1)

## Orbital Diagram

https://chemistryfigures.com/orbital-diagram

Make printable orbital diagrams for chemistry tests. Pick an element and charge and get its electron configuration drawn as arrows in boxes, following the aufbau principle, Pauli exclusion and Hund’s rule, with exceptions, noble gas cores, blanks for students and deliberate mistakes.

One atom or ion’s ground-state electron configuration drawn as up and down arrows in a square (or line) per orbital, with sublevel labels under them. The atom is z (its atomic number) and charge; the configuration is worked out from them.

### Parameters

- z (number: 1 to 118; default 8): The element’s atomic number. Rounded to a whole number.
- charge (number: -4 to 8; default 0): The ion’s charge; 0 for a neutral atom. Rounded to a whole number.
- rule (choice: real, filling. real: as they really are; filling: as the filling order predicts; default real): How exceptions are drawn.
- order (choice: filling, shell. filling: the order they fill (4s before 3d); shell: grouped by shell (3d before 4s); default filling): The order sublevels are drawn in.
- core (on/off: 1 (on) or 0 (off); default 0): Writes the noble gas core in brackets, like [Ar], and draws only the orbitals after it.
- arrows (choice: full, half. full: full arrows; half: half arrows; default full): The electrons’ arrow style.
- orbitals (choice: squares, lines. squares: a square box; lines: a line; default squares): How each orbital is drawn.
- arrangement (choice: row, energy. row: side by side, wrapping onto more rows; energy: stacked by energy, each sublevel a step higher than the one before it in filling order, with s, p, d and f in their own columns (order then changes only the written configuration); default row): How the sublevels are laid out.
- symbol (choice: text, blank, none. text: written; blank: a blank line for students; none: not drawn; default text): The element symbol (with its charge) beside the diagram.
- labels (choice: text, blank, none. text: written; blank: a blank line for students; none: not drawn; default text): The sublevel labels (1s, 2p…) under the orbitals.
- electrons (on/off: 1 (on) or 0 (off); default 1): Draws the electrons; 0 draws empty orbitals for students to fill.
- configLine (choice: text, blank, none. text: written; blank: a blank line for students; none: not drawn; default none): The written configuration (e.g. 1s² 2s² 2p⁴) under the diagram.
- extra (number: 0 to 3; default 0): How many more empty sublevels to draw after the last filled one, so electrons can be moved up into them. Rounded to a whole number.
- changes (JSON: JSON, URL-encoded; default {}): The teacher’s changes to orbitals, as JSON (see notes).
- titleMode (choice: none, text. none: no title; text: the words in title; default none): Whether a chart title is drawn across the top of the figure.
- title (text: up to 120 characters; default (empty); used when titleMode=text): The chart title’s words.
- answerKey (on/off: 1 (on) or 0 (off); default 0): Prints the answer key line under the figure, e.g. “O: 1s² 2s² 2p⁴”.

### Rules between parameters

- z is the atomic number, 1 to 118: z=26 is iron. charge is the ion’s charge (positive means fewer electrons than protons) and is never more than z.
- An ion loses its outermost electrons first, as textbooks teach, so Fe²⁺ (z=26&charge=2) is [Ar] 3d⁶, having lost both 4s electrons.
- rule=real draws exceptions such as Cr ([Ar] 4s¹ 3d⁵) and Cu as they really are; rule=filling draws every element as the filling order predicts.
- changes is URL-encoded JSON for a “which rule is broken?” question: an object from sublevel name to that sublevel’s orbitals, left to right, each one of "" empty, "u" up, "d" down, "ud" pair, "uu" two up, "dd" two down; e.g. {"2p":["ud","u",""]}. The list must have one entry per orbital (s 1, p 3, d 5, f 7) and the sublevel must be drawn (extra can draw up to 3 empty ones past the last filled). Changes that match the ground state are dropped.
- answerKey prints the species and its ground-state configuration (e.g. “Fe²⁺: [Ar] 3d⁶”) and, for a changed diagram, whether it is an excited state or not allowed and each rule it breaks.

### Examples

- [Iron, Fe, with its [Ar] noble gas core and the answer key.](https://chemistryfigures.com/orbital-diagram?z=26&core=1&answerKey=1)
- [The Fe³⁺ ion (3d⁵, having lost both 4s electrons and one 3d), its sublevels stacked by energy, with its configuration written under it.](https://chemistryfigures.com/orbital-diagram?z=26&charge=3&arrangement=energy&configLine=text)
- [Chromium, the exception [Ar] 4s¹ 3d⁵, with a blank line for students to write the configuration.](https://chemistryfigures.com/orbital-diagram?z=24&core=1&configLine=blank)
- [Nitrogen drawn breaking Hund’s rule (a pair in 2p while an orbital is empty), with the answer key naming the rule.](https://chemistryfigures.com/orbital-diagram?z=7&changes=%7B%222p%22%3A%5B%22ud%22%2C%22u%22%2C%22%22%5D%7D&answerKey=1)