Trends In Periodic Table

First ionisation energy increases in a period. Thus, the first IE of the elements of the second period should be as follows But in practice, the elements do not follow the above order. The first IE of these elements is The lower IE of B than that of Be is because in B , electron is to be removed from which is easy while in , electron is to be removed from which is difficult. The low IE of than that of is because of the half-filled orbitals in