FAQ - Avogadro's Number

Avogadro's Number

	What is Avogadro's Number?
	In the same way that there are 12 things in a dozen and 144 things in a gross, there are an Avogadro's Number of things in a mole.

The International Union of Pure and Applied Chemistry (IUPAC) defines a mole as the number of atoms in 12 grams of carbon-12. The 1998 CODATA recommended value1 for this number is 6.02214199 x 1023 and this is what the National Institute of Standards and Technology (NIST) currently uses.

In general, Avogadro's Number, often designated NA, is the "number of atoms needed such that the number of grams of a substance equals the atomic mass of the substance".

In other words, 6.02214199 x 1023 amu equals one gram.

The molecular weight, in atomic mass units (amu),

OK, so I'm a moron for putting up this page long before it's ready for prime time. But I have a great vision that one day it will actually be finished and complete. Please share in this delusion.

Additional sources:

http://scienceworld.wolfram.com/physics/AvogadrosNumber.html

http://www.carlton.paschools.pa.sk.ca/chemical/molemass/avogadno.htm

http://chem.sci.gu.edu.au/help_desk/The_Mole.htm

http://gemini.tntech.edu/~tfurtsch/scihist/avogadro.htm

http://www.wikipedia.org/wiki/Avogadro's_number

http://chemistry.about.com/library/weekly/aa111602a.htm

http://www.straightdope.com/mailbag/mavogadro.html

	Why don't all websites give the same value for Avogadro's Number?
	I have no idea.

For example:

6.0221367*1023
http://www.iupac.org/reports/1993/homann/values6.html

6.022136736*1023
http://education.jlab.org/glossary/avogrado.html

6.02214199*1023
http://www.wikipedia.org/wiki/Avogadro's_number

6.02252*1023
http://www.bartleby.com/65/av/Avogadnmb.html

6.02257*1023
http://chem.lapeer.org/Chem1Docs/MolExercise.html

6.0220*1023
http://scienceworld.wolfram.com/physics/AvogadrosNumber.html

6.023*1023
http://www.pas.rochester.edu/~ygao/phy141/Lecture25/tsld002.htm

International Council for Science CODATA- Committee on Data for Science and Technology http://www.codata.org/

And don't forget to celebrate Mole Day.

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1 Peter J. Mohr and Barry N. Taylor, "CODATA Recommended Values of the Fundamental Physical Constants: 1998," Journal of Physical and Chemical Reference Data, Vol. 28, No. 6, 1999 and Reviews of Modern Physics, Vol. 72, No. 2, 2000.