Key information
Atomic number: 
5
Atomic weight: 
10.81
Density: 
2340 kg/m³
Boiling point: 
0° K
Melting point: 
2303.16° K
Heat vapour: 
536.01 kJ/mol
Heat fusion: 
22.19 kJ/mol

Boron is classed as a metalloid; is less electronegative than non-metals to its right in the periodic table; and is usually oxidised in chemical reactions (oxygen is more electronegative).

P-type dopant within semiconductors
Lattice structure of Silicon with Boron

Boron is electron-deficient, possessing a vacant p-orbital, with only three outer electrons. Pure silicon structures, with four outer electrons share electrons in a lattice-structure. Boron is therefore used as a P-type dopant within semiconductors, as when mixed into the silicon lattice it forms "holes" in the lattice where a silicon electron has nothing to bond to. The absence of an electron creates the effect of a positive charge, hence the name P-type. Semiconductors have junctions of type N-P-N between positively and negatively charged parts. Holes can conduct current. A hole happily accepts an electron from a neighbour, moving the hole over a space. This P-type silicon is a good conductor of electricity.

Electron Shell: 
Amazon Books
Image of The Last Sorcerers: The Path from Alchemy to the Periodic Table
Author: National Academy of Sciences, Richard Morris
Publisher: Henry (Joseph) Press (2003)
Binding: Hardcover, 294 pages