Question

Why the atomic radii of Cu and Cr are very close to one another?

Answer 1

cu and cr are the exceptional case for electronic configuration there electron jumps in different energy level so this happen.

Answer 2

The greater attraction draws the electrons closer to the protons, decreasing the size of the particle. Therefore, atomic radius decreases. Down the groups, atomic radius increases. This is because there are more energy levels and therefore a greater distance between protons and electrons.

here it is your answer.