The Great Electron Exchange
📖 The Great Electron Exchange
Ionic bonding is like giving sweets away completely — one gives, one takes! Metals are like people with too many sweets (outer electrons) that they want to get rid of. Non-metals are like people who really want more sweets (need electrons for a full shell). The metal gives its outer electrons COMPLETELY to the non-metal. Unlike sharing (covalent), this is a total transfer — and both end up happier with full outer shells!
Metals are more stable without their outer electrons. They have just one, two, or three electrons in their outer shell — not enough to achieve a full-shell configuration. It takes far less energy to LOSE these few electrons than to gain enough to fill the shell. Losing outer electrons gives metal atoms the same stable electron arrangement as the nearest noble gas.
Non-metals achieve stability by gaining electrons. They're already close to a full outer shell — maybe just one or two electrons short. It takes less energy to GAIN a few electrons than to lose their existing ones. Gaining electrons gives non-metal atoms a stable full-shell configuration.
When a metal and non-metal meet, an electron transfer occurs: the metal TRANSFERS its outer electrons to the non-metal. Both atoms become ions — charged particles — and both achieve stable full outer shells (like noble gases). The result is a stable ionic compound.
You probably know from magnets that opposite poles attract. Charged particles behave the same way: positive and negative charges always pull towards each other. This pull is called electrostatic attraction.
Here's the key twist: when the metal loses electrons, it becomes positively charged (more protons than electrons). When the non-metal gains electrons, it becomes negatively charged (more electrons than protons). And what happens when positive meets negative? They attract each other with an incredibly strong electrostatic attraction. THIS is the ionic bond — not a physical link, but an electrical attraction so strong it takes enormous energy to overcome.
Chemistry glossary
- What is a cation?
- A positive ion (formed when metals lose electrons)
- What is an anion?
- A negative ion (formed when non-metals gain electrons)
Let's walk through sodium chloride (NaCl) — table salt:
Earn the mark scheme marks
🧠 Memory Aids
Metals vs Non-metals: "Metal LOSES, Non-metal GAINS" — MLNG (sounds like "Melon Juice")
CATions are Paws-itive: CAT-ions (positive) — cats have PAWS, and positive ions are like cats — they've LOST something (electrons) and want them back. Opposite: AN-ions are negative (ANother kind of ion).
Charge from Group number:
- Group 1 → +1 (e.g., Na⁺)
- Group 2 → +2 (e.g., Mg²⁺)
- Group 6 → -2 (e.g., O²⁻) — 8 - 6 = 2 short
- Group 7 → -1 (e.g., Cl⁻) — 8 - 7 = 1 short
Remember the dot-cross rules: "Brackets Outside, Charge Outside" — square brackets always go around each ion, and the charge is written OUTSIDE the bracket, not inside.
Now try it yourself
Quiz · Question 1 of 35
Which combination of elements forms an ionic compound?
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This topic in real past papers
Every real exam question we've found on ionic bonding, with a full worked answer.