Boron remarks on its crystal structure

1 Boron remarks on its crystal structure. The atomic and physical properties of boron are reported in 5.13.2 with a few data about its crystal structures in the elemental state. A few more comments will be added here in order to insert also boron in this short summary of the crystal properties of the various elements. In this general although partial picture, the peculiar characteristics of boron have indeed to be underlined. 

A typical building block used to construct several solid-state structures (boron-rich borides and allotropes of elemental boron) is the B12 icosahedron. According to King, (1993) an icosahedral B12 building block in which each of the 12 vertices contributes a single electron for an external two-electron two-centre (2e, 2c) bond to an external group implies the following electron count  

Electrons for the 12-centre core bond of the B12 icosahedron 2 electrons 

Corresponding to the total number of electrons required 38 electrons 

Considering that 12 B atoms have a total of 12X3 = 36 valence electrons, the B12 unit will be stable as the anion B j2.  

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