Question

A metal M forms as oxide having the formula M₂O₃. It belongs to third period. Write the atomic number and valency of the metal.

Answer 1

Period no. = no. of shells, so n = 3

From the formula M₂O₃ its valency is 3.

Since it is a metal, its valence shell has 3 electrons.

So its electronic configuration is 2, 8, 3

Atomic number = 13

Hence the metal is Aluminum with valency 3.