Question

Why does the size of an atom decreases when we move from left to right in a periodic table?​

Answer 1

Explanation:

Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are added to the same shell. ... The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases

Answer 2

•••●Answer●•••

Atomic radius of an atom is the distance from the centre of its nucleus and upto the valence shell of electrons. As we from left to right along a period, the atomic size goes on decreasing due to increase in effective nuclear change.

Hope it helps you...