Avogadro's number - History

Avogadro's number, also called Avogadro's Constant (NA) is a large constant used in chemistry and physics. Avogadro's number is formally defined as the number of carbon-12 atoms in 12 grams (0.012 kg) of carbon-12, which is approximately 6.023 × 1023. Historically, carbon-12 was chosen as the reference substance because its atomic mass could be measured particularly accurately. A mole is defined as Avogadro's number of particles of any kind of substance (atoms, ions, molecul ...

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• Avogadro's number - History
• Avogadro's number - Application
• Avogadro's number - Physical significance of Avogadro's number
• Avogadro's number - Additional physical relations
• Avogadro's number - Numerical value
• Avogadro's number - Connection to masses of protons and neutrons
• Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia - Avogadro's number

The value of Avogadro's number depends on the definition of the mole, which depends on the definition of the kilogram. Both definitions, especially that of the kilogram, are arbitrary: the kilogram system is currently based on the mass of a particular "standard" cylinder of metal in France. This means that the particular value of Avogadro's number is the result of convention; there is no physical reason for it. Hence, Avogadro's number is not a fundamental constant. Avogadro's number can be regarded as a conversion factor between the ...

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Avogadro's number, Avogadro's number - History, Avogadro's number - Application, Avogadro's number - Physical significance of Avogadro's number, Avogadro's number - Additional physical relations, Avogadro's number - Numerical value, Avogadro's number - Connection to masses of protons and neutrons, Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia II - Avogadro's number - Physical significance of Avogadro's number

The value of Avogadro's number depends on the definition of the mole, which depends on the definition of the kilogram. Both definitions, especially that of the kilogram, are arbitrary: the kilogram system is currently based on the mass of a particular "standard" bar of metal in France. This means that the particular value of Avogadro's number is the result of convention; there is no physical reason for it. Hence, Avogadro's number is not a fundamental constant. Avogadro's number can be regarded as a conversion factor between the micro ...

See also:

Avogadro's number, Avogadro's number - History, Avogadro's number - Application, Avogadro's number - Physical significance of Avogadro's number, Avogadro's number - Additional physical relations, Avogadro's number - Numerical value, Avogadro's number - Connection to masses of protons and neutrons, Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia II - Avogadro's number - Physical significance of Avogadro's number

At present it is not technologically feasible to count the exact number of atoms in 12 g of carbon-12, so the precise value of Avogadro's number is unknown. The 2002 CODATA recommended value for Avogadro's number is . A number of methods can be used to measure Avogadro's number. One modern method is to calculate Avogadro's number from the density of a crystal, the relative atomic mass, and the unit cell length determined from x-ray crystallography. Very accurate values of these quantities for silicon have been measured at the National Institute of Standards and Technology (NIS ...

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Avogadro's number, Avogadro's number - History, Avogadro's number - Application, Avogadro's number - Physical significance of Avogadro's number, Avogadro's number - Additional physical relations, Avogadro's number - Numerical value, Avogadro's number - Connection to masses of protons and neutrons, Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia II - Avogadro's number - Numerical value

A carbon-12 atom consists of 6 protons and 6 neutrons (which have approximately the same mass) and 6 electrons (whose mass is negligible in comparison). One could therefore think that NA is the number of protons or neutrons that have a mass of 1 gram. While this is approximately correct, the mass of a free proton is 1.00727 amu, so a mole of protons would actually have a mass of 1.00727 g. Similarly, a mole of neutrons has a mass of 1.00866 g. Clearly, 6 moles of protons combined with six moles of neutrons would have a mass ...

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Avogadro's number, Avogadro's number - History, Avogadro's number - Application, Avogadro's number - Physical significance of Avogadro's number, Avogadro's number - Additional physical relations, Avogadro's number - Numerical value, Avogadro's number - Connection to masses of protons and neutrons, Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia II - Avogadro's number - Connection to masses of protons and neutrons

Because of its role as a scaling factor, Avogadro's number provides the link between a number of useful physical constants when we move between an atomic mass scale and a kilogram (SI) scale. For example, it provides the relationship between: the universal gas constant R and the Boltzmann constant kB: R = kB NA the Faraday constant F an ...

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Avogadro's number, Avogadro's number - History, Avogadro's number - Application, Avogadro's number - Physical significance of Avogadro's number, Avogadro's number - Additional physical relations, Avogadro's number - Numerical value, Avogadro's number - Connection to masses of protons and neutrons, Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia II - Avogadro's number - Additional physical relations

At present it is not technologically feasible to count the exact number of atoms in 12 g of carbon-12, so the precise value of Avogadro's number is unknown. The 2002 CODATA recommended value for Avogadro's number is where the number in parentheses represents the one standard deviation uncertainty in the last digits of the value. A number of methods can be used to measure Avogadro's number. One modern method is to calculate Avogadro's number from the density of a crystal, the relative atomic mass, and the un ...

See also:

Avogadro's number, Avogadro's number - History, Avogadro's number - Application, Avogadro's number - Physical significance of Avogadro's number, Avogadro's number - Additional physical relations, Avogadro's number - Numerical value, Avogadro's number - Connection to masses of protons and neutrons, Avogadro's number - Avogadro's number in life

Read more here: » Avogadro's number: Encyclopedia II - Avogadro's number - Numerical value