Question

Sodium loses its lustre on exposure to air due to formation of

Answer 1

Yellowish substance called Sodium Peroxide.
Sodium also reacts with oxygen to form sodium oxide. The reactions as follows:
4Na+O2→2Na2O4Na+O2→2Na2O

2Na2O+O2→2Na2O2

Answer 2

Sodium loses its lustre due to the formation of Na2o, NaOH and Na2co3

Explanation:

Hope it helps you.