In a period from Li to F, ionisation potential

Ionization energy increases along a period with

increase in atomic number. However, in the periodic table, going from left to right, while the Ionization Potential of Li is 5.4 eV, that of Be: 9.3

eV, B: 8.3 eV, C: 11.3 eV, N: 14.6 eV, O: 13.6 eV,

and F: 17.0 eV.