Occurrence and position of boron and silicon in periodic table

Boron (B) is the first member of group 13 of the periodic table and is the only non-metal of this group. It has an electronic configuration of 1s² 2s² 2p¹ with only three electrons in its valence shell.

Dissimilarities of boron with other elements of this group are:

• Boron is a non-metal while all other elements of this group are metals.

• Boron forms only covalent compounds, while other elements of this group form both covalent and ionic compounds.

• Boron shows a maximum covalency of four, while other elements of this group show a maximum valency of six.

• Boron forms electron-deficient compounds.

These dissimilarities are due to:

• Small atomic size

• High ionization energy

• Low electronegativity.

Boron occurs in the Earth's crust to an extent of about 0.001% mainly as borates and orthoboric acid. The chief minerals of boron are:

• Borax or tincal Na₂[B₄O₅(OH)₄.8H₂O

• Colemanite Ca₂[B₃O₄(OH)₃]₂.2H₂O

• Kernite Na₂[B₄O₅(OH)₄]

Minerals rich in borates are found in California (U.S.A.) and Turkey.

Silicon is present in nature in the form of silica (SiO₂) and silicates. Rocks and clays consist of silicate minerals. Silicon is the second most abundant element (~ 27.2 wt%) on the earth's crust after oxygen {45.5wt%}.