Question

which of the following elements has the smallest atomic radius?
bromine
chlorine
selenium
sulfur

Explanation:

Atomic radius decreases across a period (from left to right) and increases down a group. Chlorine (\(Cl\)) and sulfur (\(S\)) are in period 3, bromine (\(Br\)) is in period 4, and selenium (\(Se\)) is in period 4. Among period 3 elements, \(Cl\) is to the right of \(S\). So \(Cl\) has a smaller atomic radius than \(S\). And since \(Cl\) is in a higher period (period 3) compared to \(Br\) and \(Se\) (period 4), \(Cl\) has a smaller atomic radius.

Answer:

chlorine