Why do metals form cations and non - metals form anions?

Cation and anions are formed in

How are cations and anions formed ?

How do metals and non-metals react with acids?

(a) What is Lanthanoid contraction? Give the cause of lanthanoid contraction. (b) Why do transition metals form many coloured ions?

A non - metal can form compound by

Why do alkali metals form unipositive ions and impart characteristic colours to flame?

How do metals and non-metals react with bases?