Question

Sodium Zincate is written as Na2ZnO2 but Sodium aluminate as NaAlO2. Why not Na2AlO2?

Answer 1

Valency of alo2 is one

Answer 2

Sodium Zincate is formed by Sodium cation (Na+) and Zincate anion (ZnO2-2) , thus, giving rise to the chemical formula of Na2ZnO2. Here, zincate anion has valency 2.

But sodium aluminate is formed by sodium cation (Na+) and aluminate anion (AlO-). Here, aluminate anion has valency 1.We get the formulae by the criss-crossing of the valencies.

Hope it helps. ...