What is the trend in atomic radius from left to right on the periodic table?
Atomic size decreases from left to right in the Periodic Table.
As you move from left to right, the nucleus gains protons.
This increases the positive charge of the nucleus and its attractive force on the electrons.
At the same time, electrons are added to the atoms as you move from left to right across a period.
These electrons reside in the same energy shell and do not offer complete shielding.
The effect of the increasing proton number is greater than that of the increasing electron number.
As a result, the valence electrons are held closer to the nucleus, and the atomic radius decreases.
The chart below shows the relative sizes of atoms.
The following video shows how the atomic radius of elements changes as you move across the Periodic Table.