Question

The correct order of increasing ionization energies of the following elements (Fr, Na, Cs, Rb, K)

• A. Fr < Na < Cs < Rb < K
• B. Fr < Cs < Rb < K < Na
• C. Na < K < Rb < Cs < Fr
• D. None of the above

Answer 1

The correct option is B Fr < Cs < Rb < K < Na

The ionization energy is the amount of energy required to remove the valance electron of an isolated gaseous atom to form a cation. The ionization energy increases across the period and decreases down the group.

The elements given in the question belongs to the first group. So the correct order of increasing ionization energy is:

$Fr<Cs<Rb<K<Na$