1.0 Group $13$ – The Boron Family

1.1 Physical Properties
1.2 Chemical Properties

It consists of five elements namely Boron ($B$), Aluminium ($Al$), Gallium ($Ga$), Indium ($In$) and Thallium ($Tl$). The configuration of outermost energy shell is $ns^{2}np^{1}$. Boron is a non-metal and always form covalent bonds. Normally it forms three covalent bonds at $120^°$ using $sp^2$ hybrid orbitals. The other four elements form trivalent compound. The heavier members show inert pair effect and they are more metallic and more ionic than boron. Boron is non-metallic in nature. It is extremely hard and black coloured solid. It exists in many allotropic forms. Due to very strong crystalline lattice, boron has unusually high melting point.

Rest of the members are soft metals with low melting point and high electrical conductivity. Gallium with unusually low melting point ($303\ K$), could exist in liquid state during summer. Its high boiling point ($2676\ K$) makes it a useful material for measuring high temperatures. Density of the elements increases down the group from boron to thallium.