Q29 / 110 · VITEEE 2024 · Chemistry

Which of the following order in respect to ionisation energy is correct?

  • A
    $\mathrm{N}\gt\mathrm{O}\gt\mathrm{F}$
  • B
    $\mathrm{N} \lt \mathrm{O} \lt \mathrm{F}$
  • Correct answer
    C
    $\mathrm{N}\gt\mathrm{O} \lt \mathrm{F}$
  • D
    $\mathrm{N} \lt \mathrm{O}\gt\mathrm{F}$

Solution

lonisation energy is the energy required to remove an electron from outer shell of an atom. Since, on moving from left to right in a period, size decreases, thus larger amount of energy is required to remove an electron, i.e. ionisation energy increases. Although the size of O -atom is smaller as compared to N but the ionisation energy of N is higher. This is because in case of N, the electron is to be removed from stable half filled $2 p^3$ orbital. Hence, the correct order is $N \gt O \lt F$

Hence, the correct answer is option: 'C'.

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