Earth Materials


Minerals Examinations Outline

Atoms, comprising protons (+ charge), neutrons (no charge) and electrons (-charge), are the building blocks of all materials.

Elements have a unique number of protons (eg Helium [He] has 2 protons. The number of protons determines the atomic number of an element. The number of protons and neutrons determines the atomic mass. Helium has 2 protons + 2 neutrons and an atomic mass of 4. In the element helium the +charge of the 2 protons is balanced by 2 electrons.

Some elements have atoms with different numbers of neutrons (but the same number of protons). Such atoms are called isotopes. Uranium atoms always have 92 protons. Most uranium atoms have 146 neutrons and an atomic mass of 238. Rare (0.7%) uranium atoms have 143 neutrons and an atomic mass of 235. Click here to check out some other elements.

Ions are atoms (or groups of atoms) that have a + or - charge due to the loss or gain of one or more electons. The sodium cation [Na+] has lost one electron. The chloride anion [Cl-] has gained one electron. Sodium cations and chloride anions combine to form the compound sodium chloride (common salt NaCl).

Minerals are defined as naturally occurring, inorganic substances with a narrow range of chemical composition and characteristic physical properties. The naturally occuring form of the compound sodium chloride is the mineral halite.


Minerals Examinations Outline
(c) Department of Civil and Geological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada, S7N 5A9