MCQ
The first ionization enthalpies of four consecutive elements present in the second period of the periodic table are $8.3, 11.3, 14.5$ and $13.6\,\, eV,$  respectively. Which one of the following is the first ionization enthalpy of nitrogen ?
  • A
    $13.6$
  • $14.5$
  • C
    $11.3$
  • D
    $8.3$

Answer

Correct option: B.
$14.5$
b
Elements in the 2nd period are: Period Elements II nd

Li Be BC N O F Nel In a period from left to right, ionization potential increases. But in case of nitrogen

and oxygen, nitrogen has more ionization potential than oxygen atom due to stable electronic configuration of nitrogen. $7 N=1 s^{2}, 2 s^{2} 2 p^{3} \mid$

$\uparrow\|\| \|$

(Stable configuration) $80=1 s^{2}, 2 s^{2} 2 p^{4}$ (Unstable configuration) Nitrogen has stable configuration as

the p-orbitals are half-filled completely. So, more energy is required to remove an electron from the outermost orbit of nitrogen atom. So, $\mathrm{N}_{2}$, has 14.5 value of ionisation potential.

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