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JEE Main levelSingle correct optionDifficulty 2 of 3pt140

Chlorine has a much more negative electron gain enthalpy than sulfur (-349 against $- 200 kJ mo l^{- 1}$ ) chiefly because

ACl has a lower nuclear charge than S
BCl has a larger atomic radius than S
CCl has a completely filled $3 p$ subshell before gaining the electron
DCl has a larger effective nuclear charge and attains the stable noble gas configuration $3 s^{2} 3 p^{6}$ on gaining one electron

Answer: D

Across the third period Zeff rises and the size falls, so the incoming electron is held more strongly. The added electron also completes the argon configuration for Cl, which is highly favourable. S still needs two electrons.

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