Here's why:

* Group 1: Potassium is an alkali metal and therefore belongs to Group 1 (also known as Group IA) of the periodic table.

* Higher atomic number than chlorine: Chlorine (Cl) has an atomic number of 17, while Potassium has an atomic number of 19.

* Lower atomic number than bromine: Bromine (Br) has an atomic number of 35, which is higher than Potassium's.