Boron, aluminium, gallium, indium and thallium are all members of group 13 of the periodic table. All are characterized by having 3 valency electrons. Boron, a non-metallic element, is markedly different from the other group members, all of which are silvery-white metals.
This distinction between boron and the other elements, however, extends beyond the metallic / non-metallic divide. Boron has far higher melting and boiling points than the rest of the group. Its melting point, for example, is 2092 degrees Celsius, whereas the next highest, that of aluminium, is only 660.45 degrees Celsius. All the metals melt with relative ease.
A further difference is in the levels of electrical resistivity. Boron is a poorer conductor of electricity than aluminium, and gallium and indium are semiconductors. These last two are used in electronic components. And furthermore, boron is a substance of great hardness, whereas all the metals are relatively soft.
Boron is also less reactive than the metals. At room temperatures, it combines with only fluorine.
