Why is the horizontal component of a velocity remains constant in horizontal and inclined projection

This is because there is no acceleration in the horizontal direction

Explanation:

This is because, the only acceleration affecting the object in horizontal and inclined projection is the acceleration due to gravity, which is directed the vertical downward direction. There is a velocity change only in the vertical direction and none in the horizontal direction because, there is no acceleration in the horizontal direction. So, its velocity remains constant.

helium

oxygen

neon

sodium