The atomic radius of atoms generally decreases from left to right across a period. The atomic radius of atoms generally increases from top to bottom within a group.

What are the two trends in atomic radius?

There are two main atomic radius trends.

One atomic radius trend occurs as you move left to right across the periodic table (moving within a period), and the other trend occurs when you move from the top of the periodic table down (moving within a group).

Why does atomic radius decrease from left to right?

Atomic size gradually decreases from left to right across a period of elements. ... This means that the nucleus attracts the electrons more strongly, pulling the atom's shell closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases.