Question

Which of the following element has highest electron-gain enthalpy?

• A. Oxygen
• B. Neon
• C. Chlorine
• D. Fluorine

Answer 1

The correct option is C

Chlorine

The explanationthe for correct option

(c) Chlorine

• Chlorine ($\mathrm{Cl}$) is an element of halogen group (group $17$).
• The attraction for an incoming electron decreases with the nucleus when the atomic size increases. Hence, electron gain enthalpy becomes less negative
• Therefore, chlorine has the highest electron-gainthe enthalpy.

The explanationelectron-gainelectron-gain for incorrect options

(a) Oxygen

• Oxygen ($\mathrm{O}$) is an element of chalcogen (group $16$)..
• It has compact nature with respect to chlorine.
• And halogens have the highest electron- gain enthalpy.
• Therefore, oxygen doesn't have the highest electron- gain enthalpy.

(b) Neon

• Neon ($\mathrm{Ne}$) (group $18$) being fully filled electronic configuration is stable.
• And halogens have the highest electron- gain enthalpy.
• Therefore, neon doesn't have highest electron- gain enthalpy.

(d) Fluorine

• Fluorine ($\mathrm{F}$) is an element of halogen group (group $17$).
• And generally, electron- gain enthalpy decreases down the group
• But due to small size of fluorine, it has lower value than chlorine.
• Therefore, fluorine doesn't have highest electron- gain enthalpy.

Therefore, option (c) Chlorine is correct option.