Question

The correct order of ionization energies is
(a) Zn < Cd < Hg
(b) Hg < Cd < Zn
(c) Ar > Ne > He
(d) Cs < Rb < Na

Answer 1

Answer:

D

Explanation:

Effective nuclear charge decreases down the group and I.P is directly proportional to effective nuclear charge.  

Thus, I.P decreases down the group and the correct order is Na>Rb>Cs.

Answer 2

Answer:

The correct answer is Option D: $Cs < Rb < Na$

Explanation:

• The least amount of energy necessary to remove a valence electron from a gaseous atom in isolation is known as the ionization energy.

• The atom's atomic number rises across the period, while at the same time, the number of electrons in the same valence shell rises.

• Moving downwards in a group causes the valence shell to distance itself from the nucleus, which reduces the nucleus's attraction to the test electron and lowers the ionization energy.

Explanation for the wrong options:

All other choices are false because only s-group elements may readily lose their outer shell electrons at low ionization energy.