Question

The correct order of electron gain enthalpy (most endothermic first and most exothermic last) is:
A. `Be lt B lt C lt N`
B. `Be lt N lt B lt C`
C. `N lt Be lt C lt B`
D. `N lt C lt B lt Be`

Answer 1

Correct Answer - B
`Be` and `N` has `1s^(2)2s^(2)` and `1s^(2)2s^(2)2p^(3)` stable configuration respectively. So addition of extra electron is difficult in their valence shell. The atomic size of `C` is smaller than `B` and also `C` has higher nuclear charge, so additon of electron will be easier in `C` than `B`.