Question

The element which has the least ionization potential is:

• A. Aluminium
• B. Chlorine
• C. Sodium
• D. Sulphur

Answer 1

The correct option is D

Sulphur

Explanation for correct option:

• Ionization potential is the amount of energy required to remove a valence electron from the isolated gaseous atom.
• The factor that affects ionization potential is the atomic size if the atomic size increases the potential ionization decreases.
• Ionization energy increases from left to right in a period and decreases from top to bottom in a group
• Sulphur has the least ionization energy as by losing one electron sulphur can attain a half-filled state and have greater stability.

Explanation for wrong option:

Option A:

• Aluminium has an electronic configuration$3s^2,3p^1$.
• The $3p$ electron of aluminium is farther from the nucleus, thus the effect of an increase in nuclear charge is greater in aluminium.

Option B:

• The outer orbitals of sulphur are located farther from the nucleus than the orbitals of chlorine.
• As the nucleus is more positive of chlorine it will have greater ionisation energy.

Option C:

• Lesser the distance of orbitals from the nucleus the higher the energy is required to remove the outermost electron and vice versa.
• Hence more energy is required to remove electrons hence sodium has higher ionisation energy.

Therefore the correct option is Option D