In which of the following, elements are correctly arranged in the decreasing order of their second…

In which of the following, elements are correctly arranged in the decreasing order of their second ionisation enthalpies?
  1. $\mathrm{O}>\mathrm{F}>\mathrm{N}>\mathrm{C}$
  2. $\mathrm{N}>\mathrm{O}>\mathrm{F}>\mathrm{C}$
  3. $\mathrm{F}>\mathrm{O}>\mathrm{N}>\mathrm{C}$
  4. $\mathrm{C}>\mathrm{N}>\mathrm{O}>\mathrm{F}$

Solution


As we move across a period, effective nuclear charge $\left(Z_{\text {eff }}\right)$ increases and so do the first ionisation energy, $\mathrm{F}>\mathrm{O}>\mathrm{N}>\mathrm{C}$. But after the removal of 1 electron, the second ionisation potential of oxygen becomes more than that of $\mathrm{F}$ as it acquires a half-filled stable electronic configuration. So, the correct order of second ionisation potential is $\mathrm{O}>\mathrm{F}>\mathrm{N}>\mathrm{C}$.

Asked in: AP EAMCET 2022 (07 Jul Shift 2)

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