Question

Why does carbonate have a valence of two?

Answer 1

The valency of carbonate is two because it can combine with two hydrogen atoms.

Explanation:

Valency is the number of univalent atoms (e.g., `"H"` or `"Cl"` atoms) that can combine with an atom or an ion.

The structure of carbonate is

Each `"O"` atom has a negative charge, so it can combine with an `"H"^"+"` ion to form carbonic acid.

Since carbonate can combine with two `"H"` atoms, its valency is two.