Question

As you move from top to bottom on the periodic table, what generally happens to the atomic radius?
(A) it decreases
(B) it decreases, then increases
(C) it remains constant
(D) it increases, then decreases
(E) it increases

Answer 1

Hint: On moving down the group in the periodic table, new shells are added to the atom. These are also called energy levels, and defined with the principal quantum number (n). As ‘n’ increases the valence electrons go farther from the nucleus.

Complete step by step answer: On moving from top to bottom, as the number of energy levels increases as you move down the group, the number of electrons also increases.The valence electrons occupy higher levels due to the increasing quantum number (n). Each substituent energy level is farther from the nucleus than the last. As the outer shells move away from the core nucleus, the effective nuclear charge on the outermost shell is very less, also Electron shielding prevents these outer electrons from being attracted to the nucleus, thus they are loosely held. This results in an increase in atomic radii.

Hence, the correct option is E.

Note: The shielding effect sometimes referred to as atomic shielding or electron shielding describes the attraction between an electron and the nucleus in any atom with more than one electron. The shielding effect can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces on the electrons in the atom.