Main-group element

The main-group elements are a collection of chemical elements. This is the first two and last six columns of the periodic table. Main group elements tend to have simpler chemistry than other blocks. They are often the focus of introductory chemistry.

The main group can be split by column into the alkali metals, alkali earth metals, boron group, carbon group, pnictogens, chalcogens, halogens, and noble gases.

In terms of blocks, the main group contains the s-block and p-block elements.

Properties

These elements obey the octet rule, meaning they are most stable in chemical compounds that give them eight valence electrons. The exceptions are hydrogen, helium, and lithium, which instead obey the duplet rule for period 1 elements.

Beryllium and boron are also sometimes called exceptions. Compounds like beryllium oxide and boron trifluoride do not have enough electrons to obey the octet rule with normal main group chemistry. These compounds form coordinate covalent bonds to complete their octets. This also happens in covalent lithium compounds like organolithium reagents.

Main group elements tend to have one main oxidation state, with other oxidation states separated by steps of 2.

Similar groups

The group 3 elements and group 12 elements have some properties in common with main-group elements. Like main group elements, these elements have one major oxidation state (+3 for group 3 elements, +2 for group 12).