Carbon: Molecule-maker supreme

 

Carbon: Molecule-maker supreme

Three things make carbon special. 

Covalent bonds are those within a molecule where various atoms share an electron. Those tight linkages hold the atoms close to one another. Each carbon atom can form four covalent bonds at once. That’s a lot. And it’s not just that carbon can form four bonds, but rather that it wants to form four bonds.

Carbon’s covalent bonds come in three types: single, double and triple bonds. A double bond is extra-strong and counts as two of carbon’s four desired bonds. A triple bond is stronger still, and counts as three. All these bonds and bond types allow carbon to make many types of molecules. In fact, simply replacing any single bond with a double or triple bond will give you a different molecule.

Carbon atoms tend to link up with other carbon atoms to form chains, sheets and other shapes. Scientists call this ability catenation (Kaa-tuh-NAY-shun). Plastic is the name for a family of organic polymers. Their long carbon chains can either be straight or branch out like trees. Each trunk or branch of these polymers is made from a backbone of catenated carbons. Carbon can link into ring shapes, too. Caffeine, a molecule in coffee, is a compact, two-ring, spider-shaped molecule held together by the catenation of carbon atoms. Carbon atoms even connect to form perfectly spherical 60-carbon balls. These are known as buckyballs.

Hydrocarbons: The basis of fossil fuels

Crude oil and natural gas are fossil fuels made from a complex mix of natural organic chemicals, generally known as hydrocarbons. That term is a mash-up of hydrogen and carbon. These molecules are, too.

The simplest hydrocarbon is methane (METH-ain). It’s made from a single carbon atom bonded (covalently) to four hydrogen atoms. A two-carbon version, ethane (ETH-ain), holds onto six hydrogen atoms. Add a third carbon — and two more hydrogens — and you get propane. Notice that the end of each name stays the same. Only the first part, or prefix, changes. Here, that prefix tells us how many carbons the molecule holds. (Peek at the back of a bottle of hair conditioner. Try to spot some of these prefixes hidden in the long chemical names.)

Once we reach four bound carbons, new hydrocarbon shapes become possible. Since carbon chains can branch, four carbon atoms (and their hydrogens) may bend and connect into unusual shapes. That results in new molecules.