p-Block Elements – I — Chemistry STD 12 — Question

1. The tendency of an element to form a cation by losing electrons is known as an electropositive or metallic character.
2. This character depends on the ionisation energy.
3. Generally, on descending a group the ionisation energy decreases and hence the metallic character increases.

In p-block, the elements present in the lower left part are metals while the elements in the upper right part are non-metals. Elements of group 13 have metallic characters except for the first element boron which is a metalloid, having properties intermediate between the metal and non-metals. The atomic radius of boron is very small and it has a relatively high nuclear charge and these properties are responsible for its non-metallic character.

In the subsequent groups, the non-metallic character increases. In group 14 elements, carbon is a non-metal while silicon and germanium are metalloids. In group 15, nitrogen and phosphorus are non-metals and arsenic and antimony are metalloids. In group 16, oxygen, sulphur and selenium are non-metals and tellurium is a metalloid. All the elements of groups 17 and 18 are non-metals.