The p-block contains metallic and non-metallic elements. It is very interesting to note that the non-metals and metalloids exist only in the p-block of the periodic table. The non-metallic character increases along a period but decreases down a group. In fact the heaviest element in each p-block group is the most metallic in nature. Therefore, the elements with most metallic character are located mostly in the lower left portion while those with most non-metallic character are present at the top right portion of the periodic table. In between these, there are some elements which show characteristics of both metals and non-metals and are called metalloids. The common metalloids in p-block elements are B, Al, Si, Ge, As, Sb, Te, Po, At. This change from non-metallic to metallic brings significant diversity in the chemistry of these elements.
In general, non-metals have higher ionization enthalpies and higher electronegativities than metals. Therefore, in contrast to metals which readily form cations, non-metals readily form anions. The compounds formed by combination of highly reactive non-metals, with highly reactive metals are generally ionic in nature because of large differences in their electronegativities. On the other hand, compounds formed between non-metals themselves are largely covalent in character because of small differences in their electronegativities. It can be understood in terms of their oxides. The oxides of non-metals are acidic or neutral whereas oxides of metals are basic in nature. The oxides of metalloids are amphoteric. Further more, the more electropositive the metal, the more basic is it and the more electronegative the non-metal, the more acidic is its oxide. Therefore, in p-block elements, acidic character of the oxides increases or basic character decreases along a period. Similarly, the basic character of the oxides increases or acidic character decreases down the group.
