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WHAT IS GOLD?
Gold Properties Part1
Article # : gold158
Properties
Understand more about the unique chemical and physical properties of gold that enable it to be utilised in a diverse range of practical applications
Gold, (symbol Au) has an atomic number of 79 i.e. each gold atom has 79 protons in its nucleus. The atomic mass of the gold atom is 196.967 and the atomic radius is 0.1442nm.
Interestingly this is smaller than would be predicted by theory.
The arrangement of outer electrons around the gold nucleus is related to gold's characteristic yellow colour. The colour of a metal is based on transitions of electrons between energy bands. The conditions for the intense absorption of light at the wavelengths necessary to produce the typical gold colour are fulfilled by a transition from the d band to unoccupied positions in the conduction band. Gold’s attractive warm colour has led to its widespread use in decoration
Whilst the number of protons in a gold nucleus is fixed at 79, the number of neutrons can vary from one atom to another giving a number of isotopes of gold. However, there is only one stable non-radioactive isotope accounting for all naturally found gold.
The crystal structure for metallic gold is face centred cubic FCC (see right) This crystal structure contributes to gold's very high ductility since FCC lattices are particularly suitable for allowing the movement of dislocations in the lattice. Such dislocation movement is essential for achieving high ductility.
The density of gold (19.3 gcm-3) depends on both its atomic mass and the crystal structure. This makes gold rather heavy compared to some other common materials. For example, aluminium has a density of 2.7 gcm-3 and even steel's density is only 7.87 gcm-3.
The melting point of pure gold is 1064°C, although when alloyed with other elements such as silver or copper the gold alloy will melt over a range of temperatures. The boiling point of gold, when gold transforms from the liquid to gaseous state, is 2860°C.
The ability of gold to efficiently transfer heat and electricity is bettered only by copper and silver, but unlike these metals gold does not tarnish, making it indispensable in electronics.
Source: Utilisegold.com