Chemical Bonding, Carbon Style

Chapter 4 Section 1

The Carbon Atom and Its Bonds

The atomic number of carbon is 6. This means that the nucleus of a carbon

atom contains 6 protons. Surrounding the nucleus are 6 electrons.

Of these electrons 4 are valence electrons.

Few elements have the ability of carbon to bond with both itself and other elements in so many different ways.

Carbon atoms form bonds Carbon atoms form more bonds than

most other atoms. With four valence electrons, each carbon

atom is able to form four bonds. In comparison, hydrogen, oxygen, and

nitrogen can form only one, two , or three bonds.

With four bonds to each carbon atom, it is possible to form substances with many carbon atoms, even thousands of them.

Arrangement of Carbon Atoms

It is possible to arrange the same number of carbon atoms in different ways.

Carbon atoms can form straight chains, branched chains, and rings.

Sometimes even networks of two or more rings of carbon atoms are joined together.

Look on page 113 - Figure 3

Forms of Pure CarbonBecause of the ways that carbon

forms bonds, the pure element can exist in different forms.

Diamond, graphite, and fullerene are three different forms of the element carbon.

Diamond Diamond is the hardest mineral and is

formed deep within the Earth. At very high temperatures and pressures,

carbon atoms form diamond crystals. Each carbon atom is bonded strongly to

four other carbon atoms. The result is a solid that is extremely

hard and unreactive. The melting point of diamond is over

3500 degrees Celsius. The surface of some stars are as hot as

3500 degrees Celsius.

Graphite The lead in a lead pencil is actually

graphite, another form of carbon. In graphite, each carbon atom is bonded

tightly to three other carbon atoms in flat layers.

However, the bonds between atoms in different layers are very weak, so the layers slide past one another easily.

If you run your fingers over pencil marks, you can feel how slippery graphite is.

Because of this, graphite is used as a lubricant in machines.

Fullerenes In 1985, scientists at Rice University in Texas

made a third form of the element carbon, a form that no one had identified before.

The new form of carbon consists of carbon atoms arranged in repeating patterns like the one shown in figure 6 on page 115.

Fullerene is named after the architect Buckminster Fuller who designed dome shaped buildings, called geodesic domes which some fullerenes resemble.

Scientists are looking for uses of fullerenes because of their ball-shaped appearance.

Someday, fullerenes may be used to carry medicines through the body.