Day 13

NATIVE ELEMENTS

Metal Structures -
Metals generally have one of three packing arrays, and metallic bonding:

1. cubic closest packing, in which each atom is surrounded by 12 neighbors, and a face-centered cubic lattice is defined
2. hexagonal closest packing, in which 12 surround each, and defines a hexagonal lattice
3. 'body centered cubic' packing, each is surrounded by 8 neighbors

Diamond and Graphite structures: covalently bonded structure; covalent and van der Waals's structure, contrast hardness, conductivity, etc. Diamond, covalent bonds in which each C is in tetrahedral coordination with 4 other C - high hardness, very low conductivity due to lack of free electrons Graphite, each C is covalently bonded to three other C, leaving one electron free - low hardness, Van Der Waals bonds, high electrical conductivity