conductor of heat and electricity. It
has a variety of uses including electrical contacts, high-temperature equipment, and as a solid lubricant.
Graphite mixed with clay is the ‘lead’
in pencils (hence its alternative
name). The third crystalline allotrope
is fullerite (see buckminsterfullerene). There are also several
amorphous forms of carbon, such as
*carbon black and *charcoal.
There are two stable isotopes of
carbon (proton numbers 12 and 13)
and four radioactive ones (10, 11, 14,
15). Carbon–14 is used in *carbon
dating.
Carbon forms a large number of
compounds because of its unique
ability to form stable covalent bonds
with other carbon atoms and also
with hydrogen, oxygen, nitrogen,
and sulphur atoms, resulting in the
formation of a variety of compounds
containing chains and rings of carbon atoms.
A
• Information from the WebElements site
carbon assimilation The incorporation of carbon from atmospheric
carbon dioxide into organic molecules. This process occurs during
*photosynthesis. See carbon cycle.
carbonate A salt of carbonic acid
containing the carbonate ion, CO 3
2– .
The free ion has a plane triangular
structure. Metal carbonates may be
ionic or may contain covalent
metal–carbonate bonds (complex carbonates) via one or two oxygen
atoms. The carbonates of the alkali
metals are all soluble but other carbonates are insoluble; they all react
with mineral acids to release carbon
dioxide.
carbonate minerals A group of
common rock-forming minerals containing the anion CO 3
2– as the fundamental unit in their structure. The
most important carbonate minerals
are *calcite, *dolomite, and *magnesite. See also aragonite.
carbonation The solution of carbon dioxide in a liquid under pressure.
carbon bisulphide See carbon
disulphide.
carbon black A Üne carbon powder
made by burning hydrocarbons in insufÜcient air. It is used as a pigment
and a Üller (e.g. for rubber).
carbon cycle 1. One of the major
cycles of chemical elements in the
environment. Carbon (as carbon
dioxide) is taken up from the atmosphere and incorporated into the tissues of plants in *photosynthesis. It
may then pass into the bodies of animals as the plants are eaten. During
the respiration of plants, animals,
and organisms that bring about decomposition, carbon dioxide is returned to the atmosphere. The
combustion of fossil fuels (e.g. coal
and peat) also releases carbon dioxide into the atmosphere. See illustration. 2. (in physics) A series of
nuclear reactions in which four hydrogen nuclei combine to form a helium nucleus with the liberation of
energy, two positrons, and two neutrinos. The process is believed to be
the source of energy in many stars
and to take place in six stages. In this
series carbon–12 acts as if it were a
catalyst, being reformed at the end of
the series:
12
6 C +
1
1 H →
13
7 N + γ
13
7 N →
13
6 C + e
+ + ν e
13
6 C +
1
1 H →
14
7 N + γ
14
7 N +
1
1 H →
15
8 O + γ
15
8 O →
15
7 N + e
+ + ν e
15
7 N +
1
1 H →
12
6 C +
4
2 He.
carbon dating (radiocarbon dating)
carbon assimilation
100
c
www.AzShimi.ir www.AzShimi.com
has a variety of uses including electrical contacts, high-temperature equipment, and as a solid lubricant.
Graphite mixed with clay is the ‘lead’
in pencils (hence its alternative
name). The third crystalline allotrope
is fullerite (see buckminsterfullerene). There are also several
amorphous forms of carbon, such as
*carbon black and *charcoal.
There are two stable isotopes of
carbon (proton numbers 12 and 13)
and four radioactive ones (10, 11, 14,
15). Carbon–14 is used in *carbon
dating.
Carbon forms a large number of
compounds because of its unique
ability to form stable covalent bonds
with other carbon atoms and also
with hydrogen, oxygen, nitrogen,
and sulphur atoms, resulting in the
formation of a variety of compounds
containing chains and rings of carbon atoms.
A
• Information from the WebElements site
carbon assimilation The incorporation of carbon from atmospheric
carbon dioxide into organic molecules. This process occurs during
*photosynthesis. See carbon cycle.
carbonate A salt of carbonic acid
containing the carbonate ion, CO 3
2– .
The free ion has a plane triangular
structure. Metal carbonates may be
ionic or may contain covalent
metal–carbonate bonds (complex carbonates) via one or two oxygen
atoms. The carbonates of the alkali
metals are all soluble but other carbonates are insoluble; they all react
with mineral acids to release carbon
dioxide.
carbonate minerals A group of
common rock-forming minerals containing the anion CO 3
2– as the fundamental unit in their structure. The
most important carbonate minerals
are *calcite, *dolomite, and *magnesite. See also aragonite.
carbonation The solution of carbon dioxide in a liquid under pressure.
carbon bisulphide See carbon
disulphide.
carbon black A Üne carbon powder
made by burning hydrocarbons in insufÜcient air. It is used as a pigment
and a Üller (e.g. for rubber).
carbon cycle 1. One of the major
cycles of chemical elements in the
environment. Carbon (as carbon
dioxide) is taken up from the atmosphere and incorporated into the tissues of plants in *photosynthesis. It
may then pass into the bodies of animals as the plants are eaten. During
the respiration of plants, animals,
and organisms that bring about decomposition, carbon dioxide is returned to the atmosphere. The
combustion of fossil fuels (e.g. coal
and peat) also releases carbon dioxide into the atmosphere. See illustration. 2. (in physics) A series of
nuclear reactions in which four hydrogen nuclei combine to form a helium nucleus with the liberation of
energy, two positrons, and two neutrinos. The process is believed to be
the source of energy in many stars
and to take place in six stages. In this
series carbon–12 acts as if it were a
catalyst, being reformed at the end of
the series:
12
6 C +
1
1 H →
13
7 N + γ
13
7 N →
13
6 C + e
+ + ν e
13
6 C +
1
1 H →
14
7 N + γ
14
7 N +
1
1 H →
15
8 O + γ
15
8 O →
15
7 N + e
+ + ν e
15
7 N +
1
1 H →
12
6 C +
4
2 He.
carbon dating (radiocarbon dating)
carbon assimilation
100
c
www.AzShimi.ir www.AzShimi.com