CBSE Class 11-science Answered

Given:

The metal forms an oxide of the formula M₂O₃.

Metal belongs to the 3^rd period.

Therefore, the valency of the metal is 3. The elements with a valency of 3 belong to the 13^th group of the periodic table. Thus, the given metal M belongs to the 13^th group of the modern periodic table.

It is given that the element belongs to the third period of the periodic table. The element which belongs to the 3^rd period and the 13^th group of the periodic table is aluminium.

Hence the metal M is aluminium. Its atomic number is 13. Its electronic configuration is 2, 8, 3.