Ion Courier

Ion Courier: ionic bonding, electron transfer and dot and cross diagrams

This free game is part of our AQA GCSE Chemistry (8462) course for exams in EXAM YEARS 2027-2029.

How ionic bonds form: metals lose, non-metals gain

For AQA GCSE Chemistry (spec point 4.2.1.2), when a metal atom reacts with a non-metal atom, the electrons in the outer shell of the metal atom are transferred to the non-metal atom. The metal atom loses electrons and becomes a positively charged ion. The non-metal atom gains electrons and becomes a negatively charged ion. The ions made by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0): Na⁺ is 2,8 like neon and Cl⁻ is 2,8,8 like argon.

In Ion Courier you do the transfer yourself. A courier drone lifts one outer electron at a time off a metal atom and you fly it to a non-metal atom with a gap in its outer shell. Try to take an electron from chlorine and it stretches out on the tractor beam and snaps back; try to give one to magnesium and it is pushed away. When every atom has a full outer shell, the positive and negative ions pull together. That strong electrostatic attraction between oppositely charged ions is the ionic bond: the transfer makes the ions, and the attraction is the bond.

Working out the charge from the group number

The charge on an ion relates to the group number of the element:

• Group 1 metals lose 1 electron: Li⁺, Na⁺, K⁺.
• Group 2 metals lose 2 electrons: Mg²⁺, Ca²⁺, Ba²⁺.
• Group 6 non-metals gain 2 electrons: O²⁻, S²⁻ (not 6−).
• Group 7 non-metals gain 1 electron: F⁻, Cl⁻, Br⁻, I⁻.

For metals, the charge is positive and equal to the group number. For non-metals in Groups 6 and 7, it is negative and equal to 8 minus the group number. The charges in a compound must add up to zero, so magnesium chloride is MgCl₂: (+2) + 2 × (−1) = 0. In the game’s “call for back-up” level you start with one atom of each element and call down extra atoms only when you need them, and in “scanner offline” the electrons are hidden, so you must use the group numbers to decide how many electrons to move.

Dot and cross diagrams for ionic compounds

Electron transfer is shown with a dot and cross diagram. The electrons from one atom are drawn as dots and the electrons from the other as crosses, so you can see where each electron came from. In Ion Courier the metal’s electrons really are crosses and the non-metal’s are dots, so a finished chloride ion has seven dots and one cross in its outer shell. After every compound, a Delivered card draws the exam version: the atoms with arrows showing each electron moving, then each ion in square brackets with its charge at the top right, outer shells only. Missing brackets or charges is one of the commonest ways to lose marks.

Three types of strong chemical bond

Spec point 4.2.1.1 says there are three types of strong chemical bond. Ionic bonding is between oppositely charged ions, in compounds formed from metals combined with non-metals. Covalent bonding is between atoms that share pairs of electrons, in most non-metallic elements and in compounds of non-metals. Metallic bonding is between atoms that share delocalised electrons, in metallic elements and alloys. The Bond Sort level asks you to send substances such as lithium iodide, carbon dioxide, chlorine, iron and brass through the right portal.

How to play Ion Courier

Drag from an atom to lift one electron with the drone, then let go over another atom to drop it in. You can also tap one atom and then the other, or press their number keys. There are six levels: first delivery (sodium chloride and lithium fluoride), double drop (magnesium oxide and calcium sulfide), call for back-up (magnesium chloride and potassium oxide), scanner offline (lithium oxide, barium bromide and potassium iodide), Bond Sort, and a 75 second Ion Rush. Mistakes cost points and open a short explanation with a link to the lesson. Build combos and beat your best score.

Exam tip: before you draw a dot and cross diagram, work out the charges from the group numbers and choose how many of each atom you need so the charges add up to zero. Only then start drawing.