Can someone tell me why the sky is blue?

A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we also see red and orange colours because the blue light has been scattered out and away from the line of sight.

Gases and partials scattered in the earths atmosphere. Is why the sky is blue. and there is a shorter and smaller waves are in the air.