For second period elements, the correct increasing order of first ionization enthalpy is

As we move across a period, ionisation enthalpy increases.

Reason : Increased nuclear charge and decrease in atomic radii.

However, abnormal values are observed for ‘Be’ and ‘N’ due to extra stability of half filled and fully filled orbitals.

Thus, the I.P₁ order------ $\mathrm{Li}<\underline{\mathrm{B}<\mathrm{Be}}<\mathrm{C}<\underline{\mathrm{O}<\mathrm{N}}<\mathrm{F}<\mathrm{Ne}$