Identify which atom has the smallest atomic radius. KGaBrCa

The atom with the smallest atomic radius among K (Potassium), Ga (Gallium), Br (Bromine), and Ca (Calcium) is Bromine (Br).

Here's the step-by-step process to identify this:

1. Understand the concept of atomic radius: The atomic radius is a measure of the size of an atom, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding cloud of electrons.

2. Know the trend in the periodic table: In general, atomic radius decreases across a period from left to right and increases down a given group. The atoms with the smallest atomic radii are found in the top right corner of the Periodic Table.

3. Locate the elements in the periodic table: K and Ca are in the fourth period, Ga is in the fourth period, and Br is in the fourth period.

4. Compare their positions: Moving from left to right across the period, the atomic radius decreases. Therefore, among K, Ga, Br, and Ca, Br, which is furthest to the right, will have the smallest atomic radius.