The observed general trend in ionization energies shows two slight discontinuities in each period. Examine the electron configuration at these points and explain why such a discontinuity may occur.

Answer 1

Look at the electron configurations for example One of the discontinuities happen from Be to B and the other from N to O
In both these situations
Be and N were in a stable position ( full orbital or half full orbitals)
So they need more energy to go to next level
therefore, they lost some energy and their energy level went lower.