• Covalent bond character is of major importance in this group & boron cmpds tend to resemble those of other non-metals (eg. Si) in their properties and reactions.
• Elemental boron is a network
covalent
(means bonding like
diamond or quartz)
metalloid and a semiconductor.
(cf. semiconductor is a
substance where the conductivity
increases as T is increased.)
• Aluminium, gallium, indium, and thallium are
considerably larger than boron, and are much more metallic giving compounds which are ionic in character.