Which one of the following order is correct for the first ionisation energies of the elements?

Options

A. `B lt Be lt N lt O`
B. `Be lt B lt Nlt O`
C. `B lt Be lt O lt N`
D. `B lt O lt Be lt N`

Answer

C

Explanation

Valence electronic configuration of given elements in
  `Be : 2s^(2)`
`B : 2s^(2)2p^(1)`
`N : 2s^(2) 2p^(3)`
`O : 2s^(2)2p^(4)`
Generally, first ionisation increases from left to right in a period. But Be has high IE than B since it is easy to remove `e^(-)` from 2p of B than 2s of Be. N has high IE than 'O' since it has stable configuration with half filled 2p orbitals. Therefore, the correct order is: B