The atomic radius of Li, Na and K are 1: 33A, 1. 54A and 1. 96A res pectively. Which of the following explaqins this gradation in atomic radius?

A.

electropositivity decreases from Li to Na to K

B.

electronegativity decreases from Li to Na to K

C.

the number of the electron shells increases from Li to Na to K

D.

the elements are in the same period

Correct answer is C

No explanation has been provided for this answer.