Question

How does the atomic size vary in going from $Na$ to $Cl$ in the periodic table?

Answer 1

The atomic size decreases in going from $Na$ to $Cl$ in the periodic table.

The atomic size is the average distance between the nucleus and the valence shell of an atom, and it is also known as the atomic radius.

Comparison of atomic radii of $\mathit{N}\mathit{a}$ and $\mathit{C}\mathit{l}$:

1. $\mathrm{Na}$ is at the farthest left of the second period, whereas $\mathrm{Cl}$ is at the farthest right.
2. Consequently, the atomic size decreases from left to right in a period due to the rise in nuclear charge and the resulting shrinkage of the electronic shell of the atom.
3. Hence the size decreases while one moves from $Na$ to $Cl$ in the periodic table.