Question

out of two elements X and Y which has bigger atomic radius give reason to justify your answer first X has atomic number and atomic mass 40 second why has atomic number 20 and atomic mass 40​

Answer 1

The atomic mass is double of the atomic number that's why X has a atomic mass 40 and atomic number 20

Answer 2

it's a general periodic trend

when we move from left to right of periodic table atomic radii decreases

and as we move from top to bottom atomic radii increases

hence Y has greater atomic radius then X

as X is argon and Y is calcium

and argon is in 3rd period and calcium is in 4th period