tive elements. Compounds of tellurium with nonmetals are covalent
(e.g. H 2 Te). Metal tellurides can be
made by direct combination of the elements and are ionic (containing
Te
2– ) or nonstoichiometric interstitial
compounds (e.g. Pd 4 Te, PdTe 2 ).
tellurium Symbol Te. A silvery metalloid element belonging to *group
16 (formerly VIB) of the periodic
table; a.n. 52; r.a.m. 127.60; r.d. 6.24
(crystalline); m.p. 449.5°C; b.p.
989.8°C. It occurs mainly as *tellurides in ores of gold, silver, copper,
and nickel and it is obtained as a byproduct in copper reÜning. There are
eight natural isotopes and nine radioactive isotopes. The element is used
in semiconductors and small
amounts are added to certain steels.
Tellurium is also added in small
quantities to lead. Its chemistry is
similar to that of sulphur. It was discovered by Franz Müller (1740–1825)
in 1782.
A
• Information from the WebElements site
temperature The property of a
body or region of space that determines whether or not there will be a
net Ûow of heat into it or out of it
from a neighbouring body or region
and in which direction (if any) the
heat will Ûow. If there is no heat Ûow
the bodies or regions are said to be in
thermodynamic equilibrium and at
the same temperature. If there is a
Ûow of heat, the direction of the Ûow
is from the body or region of higher
temperature. Broadly, there are two
methods of quantifying this property. The empirical method is to take
two or more reproducible temperature-dependent events and assign
Üxed points on a scale of values to
these events. For example, the Celsius temperature scale uses the freezing point and boiling point of water
as the two Üxed points, assigns the
values 0 and 100 to them, respectively, and divides the scale between
them into 100 degrees. This method
is serviceable for many practical purposes (see temperature scales), but
lacking a theoretical basis it is awkward to use in many scientiÜc contexts. In the 19th century, Lord
*Kelvin proposed a thermodynamic
method to specify temperature,
based on the measurement of the
quantity of heat Ûowing between
bodies at different temperatures.
This concept relies on an absolute
scale of temperature with an *absolute zero of temperature, at which
no body can give up heat. He also
used Sadi Carnot’s concept of an
ideal frictionless perfectly efÜcient
heat engine (see carnot cycle). This
Carnot engine takes in a quantity of
heat q 1 at a temperature T, and exhausts heat q 2 at T 2 , so that T 1 /T 2 =
q 1 /q 2 . If T 2 has a value Üxed by deÜnition, a Carnot engine can be run between this Üxed temperature and
any unknown temperature T 1 , enabling T 1 to be calculated by measuring the values of q 1 and q 2 . This
concept remains the basis for deÜning thermodynamic temperature,
quite independently of the nature of
the working substance. The unit in
which thermodynamic temperature
is expressed is the *kelvin. In practice thermodynamic temperatures
cannot be measured directly; they
are usually inferred from measurements with a gas thermometer containing a nearly ideal gas. This is
possible because another aspect of
thermodynamic temperature is its relationship to the *internal energy of
a given amount of substance. This
can be shown most simply in the
case of an ideal monatomic gas, in
which the internal energy per mole
(U) is equal to the total kinetic energy
of translation of the atoms in one
mole of the gas (a monatomic gas has
519
temperature
t
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(e.g. H 2 Te). Metal tellurides can be
made by direct combination of the elements and are ionic (containing
Te
2– ) or nonstoichiometric interstitial
compounds (e.g. Pd 4 Te, PdTe 2 ).
tellurium Symbol Te. A silvery metalloid element belonging to *group
16 (formerly VIB) of the periodic
table; a.n. 52; r.a.m. 127.60; r.d. 6.24
(crystalline); m.p. 449.5°C; b.p.
989.8°C. It occurs mainly as *tellurides in ores of gold, silver, copper,
and nickel and it is obtained as a byproduct in copper reÜning. There are
eight natural isotopes and nine radioactive isotopes. The element is used
in semiconductors and small
amounts are added to certain steels.
Tellurium is also added in small
quantities to lead. Its chemistry is
similar to that of sulphur. It was discovered by Franz Müller (1740–1825)
in 1782.
A
• Information from the WebElements site
temperature The property of a
body or region of space that determines whether or not there will be a
net Ûow of heat into it or out of it
from a neighbouring body or region
and in which direction (if any) the
heat will Ûow. If there is no heat Ûow
the bodies or regions are said to be in
thermodynamic equilibrium and at
the same temperature. If there is a
Ûow of heat, the direction of the Ûow
is from the body or region of higher
temperature. Broadly, there are two
methods of quantifying this property. The empirical method is to take
two or more reproducible temperature-dependent events and assign
Üxed points on a scale of values to
these events. For example, the Celsius temperature scale uses the freezing point and boiling point of water
as the two Üxed points, assigns the
values 0 and 100 to them, respectively, and divides the scale between
them into 100 degrees. This method
is serviceable for many practical purposes (see temperature scales), but
lacking a theoretical basis it is awkward to use in many scientiÜc contexts. In the 19th century, Lord
*Kelvin proposed a thermodynamic
method to specify temperature,
based on the measurement of the
quantity of heat Ûowing between
bodies at different temperatures.
This concept relies on an absolute
scale of temperature with an *absolute zero of temperature, at which
no body can give up heat. He also
used Sadi Carnot’s concept of an
ideal frictionless perfectly efÜcient
heat engine (see carnot cycle). This
Carnot engine takes in a quantity of
heat q 1 at a temperature T, and exhausts heat q 2 at T 2 , so that T 1 /T 2 =
q 1 /q 2 . If T 2 has a value Üxed by deÜnition, a Carnot engine can be run between this Üxed temperature and
any unknown temperature T 1 , enabling T 1 to be calculated by measuring the values of q 1 and q 2 . This
concept remains the basis for deÜning thermodynamic temperature,
quite independently of the nature of
the working substance. The unit in
which thermodynamic temperature
is expressed is the *kelvin. In practice thermodynamic temperatures
cannot be measured directly; they
are usually inferred from measurements with a gas thermometer containing a nearly ideal gas. This is
possible because another aspect of
thermodynamic temperature is its relationship to the *internal energy of
a given amount of substance. This
can be shown most simply in the
case of an ideal monatomic gas, in
which the internal energy per mole
(U) is equal to the total kinetic energy
of translation of the atoms in one
mole of the gas (a monatomic gas has
519
temperature
t
www.AzShimi.ir www.AzShimi.com