Question

Explain exception in the values of ionization enthalpy for elements of second period​

Answer 1

Answer:

the two major exceptions are in case of beryllium and nitrogen

as we go along the period ionisation enthalpy increases due to decrease in atomic size however it decreases as we go from beryllium to boron and from nitrogen to oxygen

the reason behind this is that beryllium atomic configuration is 1s2 2s2 which is highly stable due to fully filled orbitals . similarly, atomic configuration of nitrogen is 1s2 2s2 2px1 2py1 2pz1 which are again perfectly half filled orbitals and highly stable so more stability means higher value of ionisation enthalpy .