# For a given Period, which is the smallest atom?

Jul 19, 2017

The inert gases are in fact the SMALLEST atoms of their respective Periods.

#### Explanation:

Do these data support the opening statement?

Units of $\text{picometre} \equiv 1 \times {10}^{-} 12 \cdot m$ are quoted............

And as we face the Table, atomic size DECREASES across the Period from right to left, and INCREASES down a Group, a column of the Periodic Table.

The Periodic decrease is a consequence of electronic structure. Incomplete electron shells shield the nuclear charge very ineffectively. Across the Period, $Z$ wins, i.e. $\text{nucular charge}$ wins. Down a Group, shielding by other electrons wins, and atomic radii increase markedly.