Question

Which of the following statements regarding ionisation energy is correct?

• A. N > O > F
• B. N < O < F
• C. N > O < F
• D. N < O > F

Answer 1

The correct option is C N > O < F

Ionization energy is the energy required to remove an electron from the outer shell of an atom. Since, on moving from left to right in a period, size decreases, thus, a larger amount of energy is required to remove an electron, i.e., ionization energy increases.

Although the size of the O atom is smaller as compared to M but the ionization energy of N is higher. This is because, in the case of N, the electron is to be removed from half-filled $2p^3$ orbital. Thus, the order of ionization energy is $O<N<F$