Question

Amongst the elements B, Al, C and Si

the element having most negative electron gain enthalpy is:

• A. Si
• B. B
• C. C
• D. Al

Answer 1

Answer: (C)

C

Among the elements B, Al, C and Si, the element having most negative electron gain enthalpy is C.
On moving from left to right in a period, the electron affinity increases as $Z_{eff}$ increases and size decreases.
Hence, $E.A_C>E.A_B$.
On moving down the group, the electron affinity decreases as $Z_{eff}$ decreases and size increases.
Hence, $E.A_C>E.A_{Si}$.