Choose the correct increasing order of the second ionization enthalpy for the elements C , N , O and F .

Step-by-step solution

The second ionization enthalpy is the energy required to remove an electron from the unipositive ion. The valence electronic configurations of the unipositive ions are: C ⁺ : 2s² 2p¹ N ⁺ : 2s² 2p² O ⁺ : 2s² 2p³ F ⁺ : 2s² 2p⁴ Generally, ionization enthalpy increases from left to right across a period due to an increase in effective nuclear charge. However, O ⁺ has an exactly half-filled p -subshell ( 2p³ ), which provides extra stability. As a result, removing an electron from O ⁺ requires more energy than removing