Ionic Bonds: Dot & Cross Diagrams

Dot‑and‑cross diagram

Shows electron transfer between atoms

Metal atoms

Lose electrons and become positive ions

Non‑metal atoms

Gain electrons and become negative ions

Electrons lost = electrons gained

Ensures full outer shells

Ionic bond

Electrostatic attraction between oppositely charged ions

Group 1 metals

Lose 1 electron → form +1 ions

Group 2 metals

Lose 2 electrons → form +2 ions

Group 7 non‑metals

Gain 1 electron → form –1 ions

Group 6 non‑metals

Gain 2 electrons → form –2 ions

Example Na and Cl

Na loses 1e⁻ → Na⁺, Cl gains 1e⁻ → Cl⁻

NaCl diagram shows

Na⁺ with no electrons, Cl⁻ with full outer shell

Example Mg and O

Mg loses 2e⁻ → Mg²⁺, O gains 2e⁻ → O²⁻

MgO diagram shows

Mg²⁺ and O²⁻ both with full shells

Brackets in diagrams

Show ions with charges outside

Crosses and dots

Represent electrons from different atoms

Purpose of diagram

Visualise electron transfer and resulting ions

Ionic compounds

Form giant ionic lattices after bonding