As indicated above, neutral atoms have the same number of electrons as protons. But we sometimes encounter atoms that do not have the same number of protons and electrons. That is, it has one more positive charge than it has negative charges. Again, the superscript indicates the extra negative charge. We also encounter groups of atoms that have an overall charge.
Minerals have unique physical properties and are pure substances.
This ion, the silica tetrahedron , is the basic building block of all silicates. You should know the seven main groups of silicate minerals, along with their basic structures. The rest contain various ions, as indicated above. Feldspars are the most abundant minerals in the earth s crust. While you do not need to memorize the formulas for specific minerals, you should also be able to recognize the class of nonsilicate mineral from a given formula.