8/1/2023 0 Comments Gold element brittleTable 1: Chemical composition of gold alloys with color and karat numberĪs mentioned earlier, for most uses of gold the pure metal is too soft on its own and is therefore hardened by the addition of alloying elements, copper, silver, nickel, palladium and zinc.Īpart from copper, all other alloying metals to gold will tend to whiten the color and so it is possible to make karat golds that are white in color. Thus, we can understand that lower carat golds, because we can add more alloying metals, can have a wider range of colors than the higher carat golds. Adding copper to gold makes it redder and adding silver, zinc and any other metal makes gold paler. All other metals are white or grey in color. Gold is yellow and copper is red, the only two colored pure metals. In Table 1 are shown chemical compositions of different colored golds. 10K gold is the minimum karat designation that can still be called gold in the US.Įven 18 kt gold, with its 6 parts of another metal, gives jewelers the opportunity to play around with color. 10 kt gold contains 10 parts gold and 14 parts another metal(s), making it 41.7% gold.12 kt gold contains 12 parts gold and 12 parts of another metal(s), making it 50% gold. ![]() 14 kt gold contains 14 parts gold and 10 parts of another metal(s), making it 58.3% gold.18 kt gold contains 18 parts gold and 6 parts of another metal(s), making it 75% gold.The K stands for karat, the system used to state how much pure gold is found in an item: The designations 18 kt, 14 kt, or 10 kt indicate how much pure gold is present in the mix. Pure gold is generally too soft to be used for jewelry, so other metals are nearly always added to it, no matter which color of gold is being prepped for jewelry making. Proof gold is even finer, with over 99.95% purity, but it is only used for standardization purposes and is not available for jewelry.Ĭolored gold alloys are just as "real" as their golden colored counterparts. 24K gold is also called fine gold and it is greater than 99.7% pure gold. 24 karat (24K or 24 kt) gold is as pure as gold for jewelry gets. The purity or fineness of gold in the jewelry is indicated by its karat number. Gold has a Young's modulus of 79 GPa which is very similar to silver, but significantly lower than iron or steel. The Young's modulus of elasticity of a material is related to rigidity or stiffness and is defined as the ratio between the stress applied and the elastic strain it produces. Gold is also ductile and one ounce can be drawn into 80 km (50 miles) of thin gold wire (5 microns diameter) to make electrical contacts and bonding wire. However, there is only one stable non-radioactive isotope accounting for all naturally found gold. 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. Gold’s attractive warm color has led to its widespread use in decoration. ![]() ![]() The conditions for the intense absorption of light at the wavelengths necessary to produce the typical gold color are fulfilled by a transition from the d band to unoccupied positions in the conduction band. The color of a metal is based on transitions of electrons between energy bands. The arrangement of outer electrons around the gold nucleus is related to gold's characteristic yellow color. Interestingly this is smaller than would be predicted by theory. The atomic mass of the gold atom is 196.967 and the atomic radius is 0.1442nm. each gold atom has 79 protons in its nucleus. Gold, (symbol Au) has an atomic number of 79 i.e.
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