Ionic bonding happens when a metal reacts with a non-metal. The metal loses electrons to form a positive ion, and the non-metal gains electrons to form a negative ion. The oppositely charged ions are then held together by strong electrostatic forces.

What is an ionic bond?

An ionic bond is the electrostatic attraction between oppositely charged ions.

• Metals lose electrons → form positive ions (cations)
• Non-metals gain electrons → form negative ions (anions)
• These ions are held together in an ionic compound
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Example: Sodium and Chlorine

Sodium (Na)

• Atomic number = 11 → electron structure = 2,8,1
• It loses 1 electron → forms Na⁺ (2,8)

Chlorine (Cl)

• Atomic number = 17 → electron structure = 2,8,7
• It gains 1 electron → forms Cl⁻ (2,8,8)

The ionic bond: Na⁺ and Cl⁻ attract
→ NaCl (sodium chloride) is formed

Electron transfer diagram (description)

• Sodium with one outer electron (cross), chlorine with seven outer electrons (dots)
• Electron from sodium transferred to chlorine
• Resulting ions: Na⁺ and Cl⁻ with full outer shells

More examples

Note: Charges must balance to form a neutral compound.

Properties of ionic compounds

• Form giant ionic lattices – a regular repeating structure of ions
• Have high melting and boiling points – due to strong ionic bonds
• Conduct electricity when molten or dissolved – ions are free to move
• Do not conduct when solid – ions are fixed in place