Facts of the Matter: Element and compound are separated by 1 letter

Among the many similar but very different mistakes that I see in media is the distinction between silicon and silicone. That “e” on the end looks benign, but it makes a big difference in the material.

Absurdities such as “silicon breast implant” (ouch!) rob credibility from the infomercials.

Silicon (no “e”) is a chemical element, one of 92 naturally occurring elements that are the building blocks of all matter.

Silicon is the second most abundant element in Earth’s crust after oxygen. It never occurs in the uncombined state, as it is always locked in a tight chemical bond with oxygen. It is in the same column of the periodic table as carbon, which means that it has four sites for chemical bonds.

Carbon prefers to bond with hydrogen, allowing for the formation of fossil fuels such as petroleum and natural gas. Silicon has a special relationship with oxygen that is responsible for the hardness and durability of rocks and other silicon compounds.

Carbon will bond with oxygen to form carbon dioxide or carbon monoxide. The electronic properties of the carbon and oxygen atoms dominate to form electrically neutral molecules.

The special relationship that silicon shares with oxygen is based on the size of the silicon and oxygen atoms, which dominates the electrical neutrality of the resulting molecule.

Silicon is a relatively small atom. It is small enough to fit inside a tetrahedron of four oxygen atoms. This tetrahedral packing of the atoms builds a stable molecule that has an excess of four electrons to form the “silica tetrahedron” with a minus-4 charge.

This bond between silicon and oxygen is extremely strong and difficult to break. As a result, most silicate minerals, such as quartz, are hard and durable. As one might expect, with silicon and oxygen being the two most common elements in Earth’s crust, silicate minerals are the most common in rocks, whether igneous, sedimentary or metamorphic.

Elemental silicon must be extracted from silicate minerals (usually quartz) in order to create the semiconducting silicon that is the basis for the electrical components that comprise microchips used in virtually all electronics on the market today.

Silicone (with an “e”) is a different story. It is a collective term for a wide variety of manufactured products. All silicones consist of long molecules of alternating silicon and oxygen atoms frequently combined with carbon and/or hydrogen.

Silicones share many properties with natural rubber, such as elasticity. Different side chains attached to the main silicon-oxygen chain determine the properties of the resulting silicone, from sealant to lubricant.

Silicone has a variety of uses depending on its composition. The list is too long to detail here, but uses fall into broad categories: automotive, coatings, cookware, defoaming, dry cleaning, electronics, fire-stops, lubricants, medicine, mold making, ophthalmology, personal care, plumbing and building construction, toys and hobbies, sex toys and lubricants.

To summarize, silicon is a hard, crystalline, semimetallic substance that in pure form resembles shiny, silvery, anthracite coal. In combined form, it makes minerals such as quartz and olivine.

Silicone by contrast is an elastic, rubbery compound made from silicon-oxygen chains and industrially formulated into a wide diversity of uses.

It is easy to confuse items that sound so much alike, but that “e” on the end makes all the difference.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.