properties of carbon

how many bonds

Carbon can form single, double, or even triple bonds with other carbon atoms. In a single bond, two carbon atoms share one pair of electrons. In a double bond, they share two pairs of electrons, and in a triple bond they share three pairs of electrons. Examples of compounds with these types of bonds are shown in Figure 9.3.

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monomers and polymers of carbon

Because of carbons ability to form so many covalent bonds, it often forms polymers. A polymer is a large molecule that consists of many smaller molecules joined together by covalent bonds. The smaller molecules are called monomers. (The prefix mono means "one," and the prefix poly means "many.") Polymers may consist of just one type of monomer or of more than one type. Polymers are a little like the strings of beads in Figure 9.4. What do the individual beads represent? Many polymers occur naturally. You will read about natural polymers in this chapters "Hydrocarbons" and "Carbon and Living Things" lessons. Other polymers are synthetic. This means that they are produced in labs or factories. Synthetic polymers are created in synthesis reactions in which monomers bond together to form much larger compounds. Plastics are examples of synthetic polymers. The plastic items in Figure 9.5 are all made of polythene (also called polyethylene). It consists of repeating monomers of ethene (C2 H4 ). To learn more about polymers and how they form, go to this URL: (2:13).

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kqed properties of plastic

Exploratorium Staff Scientist Julie Yu changes and manipulates the physical and chemical properties of plastic bottles by exposing them to heat. This is how plastic bags and bottles can be recycled and used over and over again. For more information on properties of plastic, see http://science.kqed.org/quest/video/quest-lab-properties-of-plas MEDIA Click image to the left or use the URL below. URL:

forms of carbon

Pure carbon can exist in different forms, depending on how its atoms are arranged. The forms include diamond, graphite, and fullerenes. All three forms exist as crystals, but they have different structures. Their different structures, in turn, give them different properties. You can learn more about them in Table 9.1. atoms affect the properties of the substances formed? Structure Diamond crystal Description Diamond Diamond is a form of carbon in which each carbon atom is bonded to four other carbon atoms. This forms a strong, rigid, three- dimensional structure. Diamond is the hardest natural substance. It is used for cutting and grinding tools as well as for rings and other pieces of jewelry. Graphite Graphite is a form of carbon in which carbon atoms are arranged in layers. Bonds are strong between carbon atoms within each layer but relatively weak between atoms in different layers. The weak bonds between layers allow the layers to slide over one another. This makes graphite relatively soft and slippery. It is used as a lubricant. It also makes up the "lead" in pencils. Fullerene A fullerene (also called a bucky- ball) is a form of carbon in which carbon atoms are arranged in hol- low spheres. Each carbon atom is bonded to three others by sin- gle covalent bonds. The pattern of atoms resembles the pattern on the surface of a soccer ball. Fullerenes were first discovered in 1985. They have been found in soot and me- teorites. Possible commercial uses of fullerenes are under investiga- tion. To learn how this form of carbon got its funny names, go to this URL: This metal cutter has a diamond blade.

carbon bonding

Because it has four valence electrons, carbon needs four more electrons to fill its outer energy level. It can achieve this by forming four covalent bonds. Covalent bonds are chemical bonds that form between nonmetals. In a covalent bond, two atoms share a pair of electrons. By forming four covalent bonds, carbon shares four pairs of electrons, thus filling its outer energy level. A carbon atom can form bonds with other carbon atoms or with the atoms of other elements. Carbon often forms bonds with hydrogen. You can see an example in Figure 9.2. The compound represented in the figure is methane (CH4 ). The carbon atom in a methane molecule forms bonds with four hydrogen atoms. The diagram on the left shows all the shared electrons. The diagram on the right represents each pair of shared electrons with a dash (). This type of diagram is called a structural formula.

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valence electrons and bonding in carbon

Carbon is a nonmetal in group 14 of the periodic table. Like other group 14 compounds, carbon has four valence electrons. Valence electrons are the electrons in the outer energy level of an atom that are involved in chemical bonds. The valence electrons of carbon are shown in Figure 9.1.

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instructional diagrams

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questions

Cellulose is

-->  a. one of the most common compounds on Earth.

b. made by the cells of plants and animals.

c. a monomer of carbon.

d. all of the above

How many more valence electrons does carbon need to fill its outer energy level?

a. 1

b. 2

c. 3

-->  d. 4

Which type(s) of bonds can a carbon atom form with other carbon atoms?

a. single bonds

b. double bonds

c. triple bonds

-->  d. all of the above

How many bonds can each carbon atom form?

a. 1

b. 2

c. 3

-->  d. 4

Forms of pure carbon include

a. methane.

b. cellulose.

-->  c. diamond.

d. two of the above

The plastic called polythene consists of

a. repeating monomers of ethene.

b. only carbon and hydrogen atoms.

c. many fullerenes joined by covalent bonds.

-->  d. two of the above

Forms of crystalline carbon include

a. cotton.

-->  b. graphite.

c. charcoal.

d. methane.

One of the most common naturally occurring compounds on Earth is

a. graphite.

b. fullerene.

-->  c. cellulose.

d. polythene.

The monomers in a polymer may be

a. all the same.

b. different from one another.

c. joined by metallic bonds.

-->  d. two of the above

Which statement about carbon is false?

a. It has four valence electrons.

b. It forms covalent bonds with other nonmetals.

c. It is found in the majority of known compounds.

-->  d. It rarely forms large compounds called polymers.

All carbon polymers are

a. naturally occurring.

b. produced in labs.

c. found in plastics.

-->  d. large molecules.

large molecule that consists of many smaller molecules joined together by covalent bonds

a. monomer

-->  b. polymer

c. cellulose

d. diamond

e. methane

f. graphite

g. fullerene

form of carbon in which carbon atoms are arranged in layers

a. monomer

b. polymer

c. cellulose

d. diamond

e. methane

-->  f. graphite

g. fullerene

one of the simplest carbon compounds

a. monomer

b. polymer

c. cellulose

d. diamond

-->  e. methane

f. graphite

g. fullerene

form of carbon that it is the hardest natural substance

a. monomer

b. polymer

c. cellulose

-->  d. diamond

e. methane

f. graphite

g. fullerene

Carbon is a nonmetal in group 12 of the periodic table.

a. true

-->  b. false

small molecule joined with other small molecules by covalent bonds to form a much larger molecule

-->  a. monomer

b. polymer

c. cellulose

d. diamond

e. methane

f. graphite

g. fullerene

A structural formula uses dots to represent electrons.

a. true

-->  b. false

form of carbon in which carbon atoms are arranged in hollow spheres

a. monomer

b. polymer

c. cellulose

d. diamond

e. methane

f. graphite

-->  g. fullerene

All carbon polymers are made in labs or factories.

a. true

-->  b. false

carbon compound found only in plants

a. monomer

b. polymer

-->  c. cellulose

d. diamond

e. methane

f. graphite

g. fullerene

Graphite is used as a lubricant because it is slippery.

-->  a. true

b. false

Each molecule of methane contains four atoms of carbon.

a. true

-->  b. false

The chief component of cellulose is carbon.

-->  a. true

b. false

Carbon forms more compounds than any other element.

-->  a. true

b. false

Carbon can form bonds with any other element except itself.

a. true

-->  b. false

The carbon compound with the formula CH4 is polyethylene.

a. true

-->  b. false

In a triple bond, two atoms share three valence electrons.

a. true

-->  b. false

Plastics are examples of synthetic carbon polymers.

-->  a. true

b. false

All forms of crystalline carbon have the same structure.

a. true

-->  b. false

Carbon can combine only with hydrogen and oxygen.

a. true

-->  b. false

Carbon forms ionic bonds with other nonmetals.

a. true

-->  b. false

There are millions of known carbon compounds.

-->  a. true

b. false

diagram questions

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