Question

For a given Period, which is the smallest atom?

Answer 1

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

Explanation:

Do these data support the opening statement?

Units of `"picometre"-=1xx10^-12*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. `"nucular charge"` wins. Down a Group, shielding by other electrons wins, and atomic radii increase markedly.