Electronic configuration and Oxidation states
In p–block elements the last electron enters the outermost 'p' orbital. The inner core of the electronic configuration may, however, differ.
The difference in inner core of elements greatly influences their physical properties (such as atomic and ionic radii,
ionization enthalpy, etc.) as well as chemical properties.
Consequently, a lot of variation in properties of elements in a group of p–block is observed.
The maximum oxidation state shown by a p–block element is equal to the total number of valence electrons
(i.e., the sum of the s and p–electrons). Clearly, the number of possible oxidation states increases towards the right of the periodic table.
In addition to this p–block elements may show other oxidation states which normally,
but not necessarily, differ from the total number of valence electrons by unit of two.
The important oxidation states exhibited by p–block elements are shown in the Table on right side.
In boron, carbon and nitrogen families the group oxidation state is the most stable state for the lighter elements in the group.
However, the oxidation state two unit less than the group oxidation state becomes progressively more stable for the heavier elements in each group.
This is sometimes attributed to the 'inert pair effect'. The relative stabilities of these two oxidation states, group oxidation state and two unit less than the group oxidation state, may vary from group to group. It is interesting to note that the non–metals and metalloids exist only in the p–block of the periodic table.