Q9 / 90 · JEE Main 2012 (26 May Online) · Chemistry

Which of the following presents the correct order of second ionization enthalpies of $\mathrm{C}, \mathrm{N}, \mathrm{O}$ and $\mathrm{F}$ ?

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

Solution

In a period the value of ionisation potential increases from left to right with breaks where the atoms have some what stable configuration. After removing an $e^{-}$ oxygen will acquire stable configuration. Hence $\mathrm{O}^{+}$has highest second ionisation enthalpy than $\mathrm{F}^{+}$and $\mathrm{N}^{+}$. $\therefore$ correct order is $\mathrm{O}>\mathrm{F}>\mathrm{N}>\mathrm{C}$

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

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