Silicon Is an Element
All matter in the universe is formed from the 107 or so chemical elements known to exist. A chemical element is the simplest form of matter, a fundamental substance that consists of only one kind of atom. Silicon is the second most common element in the Earth's crust, second only to oxygen, and together silicon and oxygen make up approximately 75% of the Earth on which we live and from which we get all that we use in our daily lives.

Strictly speaking, silicon (whose chemical symbol is Si) is classified as a nonmetal, but it possesses some of the properties associated with metals. There are eight elements, in fact, that fall on the borderline between metals and nonmetals. Some scientists refer to these as metalloids.

One property associated with metals, for example, is their ability to conduct electricity. Silicon's electronic capabilities are unusual: At high temperatures, it acts like a metal and conducts electricity, but at low temperatures, it acts like an insulator and does not. It is said to be a semiconductor. This unusual property made silicon the perfect element to move technology first into the world of transistors, then into the world of integrated circuits, and finally into the world of today's computer chip.

Silicon is the backbone of the computer chip. The pure silicon needed for this use, however, does not exist in nature; it is formed from silica sand. Thin slices of pure silicon are then etched with the intricate electronic circuits needed to run the computer 

Silicates Are Compounds Of Silicon and Oxygen Plus Other Elements

When silicon and oxygen bond with other elements, they do so in a paired formation.

Scientists call this pairing the silicon-oxygen (SiO4 ) tetrahedron because it is made of four oxygen atoms and one silicon atom. Tetrahedron means “four surfaces” and refers to the shape of the SiO4  compound. The silicon-oxygen tetrahedron bonds most frequently with sodium, potassium, calcium, magnesium, iron, and aluminum to form silicates.

Silicates constitute the most abundant class of minerals. Geologists regard silicate minerals as the basic materials out of which most rocks are created.

Silicones Are Synthetic Compounds

Silicones are polymers, a type of synthetic compound. Developed commercially during World War II, siIicones are formed from two or more siIicon atoms linked with carbon compounds (referred to as organic compounds). Most silicones contain oxygen as well. Unlike what happens

when silica and silicates form, in siIicone, the siIicon and oxygen do not take the tetrahedral shape but instead form chain-like structures called silicon polymers. Polymerization is a chemical reaction in which small organic molecules combine to form larger molecules that contain repeating structural units of the original molecules.

Silicones can range from liquids (used as water repellents and defoamers) to greases and waxes (used as water- and heat-resistant lubricants) to resins and solids (used to make special heat- and chemical-resistant products including paints, rubbers, and plastic parts). Probably silicone's most highly publicized use is in the manufacture of breast implants.