How would you account for the irregular of ionisation enthalpies (first) in the first series of the transition elements?

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of transition elements?

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements ?

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements ?

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?

How would you account for the irregular variation of ionization enthalpies (first and second) in the first series of the transition elements ?