EOSC 118 Lecture Notes - Lecture 7: Ionic Radius, Formula Unit, Relative Atomic Mass
4 Aug 2015
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Document Summary
Most minerals are compounds, and a few are single native elements. The chemical approach to minerals helped scientists create synthetic gems. Some are accepting of synthetic minerals, some are not. Minerals have distinct properties such as chemical composition (formula) Formula includes the component elements and the # of atoms of each element in subscript. All compounds, including minerals, must be charge neutral (+ and balanced) The amount of a cation is reported in weight percent of its oxide form: see how many metal ions can be matched up with the oxygen ion. Atom basis: sio2 has 3 apfu: 1 atom of si and 2 atoms of o. It is 33% si (1 si for every 3 total atoms), and 66% o (2/3) per formula unit. Atomic weight basis: look up atomic masses of each element, then add them all together, calculate the relative weights of each element over the total mass x100%
