Ionic Compound

Key Stage 4

Meaning

An ionic compound is a molecule formed from 2 or more elements which have transferred electrons to become ions.

About Ionic Compounds

Ionic compounds form when atoms lose one or more electrons to become a positive ions and other atoms gain electrons to become negative ions. The electrostatic force of attraction between these ions is a strong chemical bond.

Metal elements form positive ions because it is easier for them lose electrons than gain electrons to get a full outer shell. Metals are on the left hand side of the Periodic Table and usually have either 1, 2, 3 or 4 electrons in the Outer Shell.

Group 1 Elements all form +1 ions; Li⁺¹, Na⁺¹, K⁺¹

Group 2 Elements all form +2 ions; Be⁺², Mg⁺², Ca⁺²

Group 3 Elements all form +3 ions; Al⁺³

Transition Metal Elements can form different ions which are shown by Roman Numerals; Iron can form Fe(II) which is Fe⁺² or Fe(III) is Fe⁺³,

Manganese can form Mn(II) which is Mn⁺² or Mn(IV) which is Mn⁺⁴

Non-metal elements form negative ions because it is easier for them to gain electrons than lose electrons to get a full outer shell. Non-metals are on the right hand side of the Periodic Table and usually have 4, 5, 6, 7 or 8 electrons in their outer shell.

Group 5 Elements all form -3 ions; N^-3, P^-3

Group 6 Elements all form -2 ions; O^-2, S^-2

Group 7 Elements all form -1 ions; F^-1, Cl^-1

Some compounds can form negative ions; Carbonate forms -2 ions CO₃^{-2, Sulphate forms -2 ions SO₄-2, Nitrate forms -1 ions NO₃-1}