Characteristics of p-Block Elements

The p-block spans groups 13 to 18. Together with the s-block, its elements are called the 'representative' or 'main group' elements (as opposed to the transition and inner-transition elements of the d- and f-blocks). The last p-block group, group 18, is the family of noble (inert) gases — their closed valence shells (a complete duplet for helium, complete octets for the rest) give them very low chemical reactivity. Group 17 (the halogens) and group 16 (the chalcogens) are reactive nonmetals whose highly negative electron gain enthalpies mean they readily gain one or two electrons to form stable, octet-complete anions ($X^-$ or $X^{2-}$). Uniquely among the four blocks, the p-block itself contains all three traditional classes of element: metals occupy its left portion, nonmetals its right portion, and metalloids sit along the zig-zag 'staircase' line that separates the two (see Fig. 7.1). Nonmetallic character increases moving left to right across the p-block within …