Atomic Structure

Valency, Oxidation State and Ionic Compounds.

When a metal reacts with a non-metal, 
the metal will lose electrons to form a positive ion
and the non-metal will gain electrons to form a negative ion.

The compound which is formed will be ionic.
It will form a giant structure (also called a giant ionic lattice).
If you do not know whether an element is a metal or
a non-metal see the periodic table.

The valency (combining power) of a metal is the same
as its oxidation state (the charge on the ion).

The number of electrons that a metal will lose
is the same as its group number in the periodic table.
A metal in group 1 will form a 1⁺ ion
(Valency 1, oxidation state 1⁺).
A metal in group 2 will form a 2⁺ ion
(Valency 2, oxidation state 2⁺).

The number of electrons that a non-metal will gain
will be 8 minus its group number.
A non-metal in group 6 will form a 2^- ion
(Valency 2, oxidation state 2^-).
A non-metal in group 7 will form a 1^- ion
(Valency 1, oxidation state 1^-).
A non-metal ion is negative because it has gained electrons.

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