Boron has electronic configuration [He]2s22p1, and main formal oxidation state +3.
Its bonding is mainly covalent, and it forms compounds with three bonds, and therefore six electrons in its valence shell: It is electron deficient.
The bonding orbitals are sp2 hybrid orbitals, and the remaining p-orbital on B acts as a pi-acceptor orbital, eg. in BF3 , where the back donation of p-electrons from F to B forms pπ-pπ bonds.
Ionic interactions also occur, and lead to a shortening and strengthening of bonds, eg. in BF4– , where pπ-pπ bonds are absent.
Occurrence
Main sources of Boron are hydrated oxides, like borax (Na2B4O5(OH)4.8H2O). Aluminium, the second element in Group 13, has the primary ore bauxite, containing hydrated aluminium oxide (Al2O3.H2O).
| The π-acceptor nature of B dominates its behavior as a Lewis acid, eg. in the reaction with tri-methylammonium. |