Minerals are chemical compounds that are composed of different elements. An element is composed of identical atoms. Atoms stick together through a phenomenon called bonding. We’ll look at atomic structure and bonding.

Dense center of atom = nucleus positive charge = proton(P) no charge = neutron (N)

Tiny electrons (e-) orbit the nucleus. Atoms have an equal # of e- and P. When an atom gains or loses an e-, it’s called an ion. Extra e- = negative charge = anion. Too few e- = positive charge = cation.

a. Ionic bonding: one or more e-s are transferred between atoms, making positive and negative ions that attract each other. 27

b. Covalent bonding: atoms can share one or more e-s. 28

Minerals are naturally occurring chemical compounds composed of atoms/ions that are bonded together.

Atoms of the same element (same # of P) can have different numbers of neutrons. These variants are called isotopes of that element. Some isotopes are stable, like ¹⁸O, ¹⁶O, ¹⁴C, and ¹²C. Other isotopes are unstable and undergo radioactive decay, like ²³⁸U, ²³⁵U, ²³²Th, and ⁴⁰K.

Radioactive decay of these and other unstable isotopes is the basis of the absolute dating of rocks.