In which of the following arrangements, the order is not according to the property indicated after it in the bracket? (Manipal 2009)

Ionization energy is the amount of energy required to remove an electron from a neutral gaseous atom. The given order B < C < N < O is incorrect because nitrogen has a higher first ionization enthalpy than oxygen. This is due to the half-filled stability of p- orbitals in nitrogen. Therefore, the correct order of the first ionization energy is B < C < O < N .