Dot-and-Cross Diagram draws the bonding diagrams UK, GCSE and Cambridge IGCSE courses use. Each atom’s shell is a circle with its element symbol in the middle, and each electron is a dot or a cross, depending on which atom it came from. Type a molecule like H2O, CH4, CO2 or ethene and the bonded atoms’ circles overlap, with each shared pair in the overlap, one electron from each atom. Type an ionic compound like NaCl, MgCl2 or Al2O3 and each ion is drawn in square brackets with its charge, the electrons the non-metal gained in the metal’s mark. Type one element, like Na or Cl-, for its atom or ion with every shell.
Teachers use it for “draw the dot-and-cross diagram” questions and their answers: leave the electrons off so students draw them, leave the charges blank, and print an answer key with each atom’s bonding and lone pairs, or the electrons moved and each ion’s arrangement, like Mg²⁺ 2,8 and Cl⁻ 2,8,8. For a “find the mistake” question, click an electron, symbol or charge in the figure to change it.
Copy the figure straight into a test, worksheet or slide, or download it as a PNG or SVG. Printing the page prints
just the figure. Share link copies the page’s address with your settings in it, so anyone who opens it sees this
exact figure, and presets save settings you use often in your browser. It’s free, with no sign-up.
Which electrons are dots and which are crosses?
In a molecule the central atom’s electrons are dots and the outer atoms’ crosses; a third kind of atom, like the O in CH₃OH or the N in HCN, gets open circles. When two atoms of one element bond, as in Cl₂ or N₂, one has dots and the other crosses. In an ionic compound the metal’s electrons are crosses and the non-metal’s dots, so the electrons a non-metal gains are crosses. Swap trades dots and crosses if your class does it the other way round.
How is a metal ion drawn?
With the full shell it’s left with after losing its outer electrons, as most mark schemes draw it: Na⁺ is a ring of 8 crosses, or 2 and 8 with every shell drawn. A non-metal ion has a full outer shell of its own electrons and the ones it gained. Each ion goes in square brackets with its charge at the top right.
How are compounds like MgCl₂ and Al₂O₃ laid out?
With up to three ions, every ion is drawn, the single ion in the middle: Cl⁻ Mg²⁺ Cl⁻. Bigger compounds are drawn as one of each ion with its number in front, as 2[Al]³⁺ 3[O]²⁻. You can switch either to the other layout.
Which molecules can it draw?
Every molecule on the Cambridge IGCSE list, H₂, Cl₂, HCl, H₂O, CH₄, NH₃, O₂, N₂, CO₂, C₂H₄ and CH₃OH, and most others where each atom shares one electron per bond, like HCN, PCl₃, H₂S or BF₃. Molecules with two carbons, like ethane and ethanol, draw too. Molecules that need a dative bond, like CO, SO₂ and O₃, polyatomic ions like NH₄⁺, and atoms with more than eight electrons, like SF₆, aren’t drawn yet; the Request it button asks us to add one.
Why are the H circles smaller in ethane?
Every circle is the same size wherever that fits, as mark schemes draw them. In ethane, ethanol and a few others, the H atoms on neighboring atoms would overlap each other, so every H circle in that molecule is drawn a little smaller, just enough to keep them apart, with each shared pair still inside its overlap.
Why does it refuse MgCl?
An ionic compound’s charges must balance. Each ion’s charge comes from its group, so Mg²⁺ needs two Cl⁻ ions. The page says what would balance: MgCl₂.
Can I make a diagram with a mistake for students to find?
Yes. Click an electron in the figure to make it a dot, a cross, an open circle, an open square or nothing, click an element symbol to leave it blank, or click an ion’s charge to show it, leave a blank box or leave it off. Reset edits puts it back. The answer key still describes the correct diagram, with a line saying the figure was edited by hand. Changing the formula, the layout or the shells clears the edits, but Swap and color keep them.
Can it draw a single atom’s electron arrangement?
Yes. Type an element from H to Ca, like Na, for its atom with every shell (2, 8, 1), or its ion, like Na+ or Cl-, in brackets with its charge. An anion’s gained electrons are crosses.
Chemistry Figures Dot-and-Cross Diagram