Caesium is the most reactive metal in the alkali metal series because

Options

A. it exerts considerable attractive force on valence electrons
B. it is a heavier metal
C. its incomplete shell is nearest to the nucleus
D. its valence electron has the highest principal quantum number than the valence electron of any of the others.

Answer

d

Explanation

When valence electron is in the highest quantum shell, the ionisation energy is lowest and hence, reactivity is highest.