Question

what is the ratio of nuclear radii of H and Al?

Answer 1

Radius of an electron is given by 0.529 X n2/z

Lets take two cases:(1) and (2)
Case 1, n=1
Radius of electron in hydrogen atom= 0.529 x 1/1
Radius of electron in helium atom= 0.529 x ½
Ratio of these radius= 1:1/2

Case 2, n=2
Radius of electron in hydrogen=0.529 x 4/1
Radius of electron in helium= 0.529 x 4//2
Ratio of these radii= 1:1/2

Thus the ratio is always the same which 2:1(H:He)

Answer 2

1:3 is the ratio of nuclear radii of H and Al. Hope it helps you