Question

Among the following which has the smallest atomic radius
Be,Al,P,I

Answer 1

Be has the smallest radius as it has electronic configuration - 1s²2s². Al has 1s²2s²2p⁶3s²3p¹. P has 1s²2s²2p⁶3s²3p³. I has
1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁵

Thus Be has only less atomic radius as it has less number of shells.