PPT Slide

Atomic Mass Scale

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• The mass of an atom is most easily expressed relative to the  mass of a chosen atomic standard.

• The modern atomic mass standard is the carbon-12 atom,  whose mass is defined as exactly 12 atomic mass units.

• One atomic mass unit (amu) is defined as 1 ¼12 the mass of a  carbon-12 atom.

• Using this standard, the 1H atom has a mass of 1.008 amu.

• The name amu has recently been changed to the dalton (D);  thus, one 12C atom has a mass of 12 daltons (12 D).

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