Atomic mass constant

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Fundamental physical constant


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The atomic mass constant, denoted by the symbol mu, is a fundamental physical constant that is used to express the masses of atoms and molecules. It is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and it is approximately equal to 1.66053906660(50) × 10−27 kilograms.

Definition[edit | edit source]

The atomic mass constant is defined as:

mu = \( \frac{1}{12} \) m(\text{C}12)

where m(\text{C}12) is the mass of a carbon-12 atom. This definition ensures that the atomic mass of carbon-12 is exactly 12 atomic mass units (u).

Importance in Chemistry and Physics[edit | edit source]

The atomic mass constant is crucial in the fields of chemistry and physics because it provides a standard for expressing atomic and molecular masses. It allows scientists to compare the masses of different atoms and molecules on a relative scale, known as the atomic mass unit (amu) or dalton (Da).

Relationship with Avogadro's Number[edit | edit source]

The atomic mass constant is related to Avogadro's number (NA), which is the number of atoms in one mole of a substance. The relationship is given by:

mu = \( \frac{M}{N_A} \)

where M is the molar mass of a substance. This relationship is fundamental in converting between the macroscopic scale of grams and the microscopic scale of atomic mass units.

Applications[edit | edit source]

The atomic mass constant is used in various applications, including:

Also see[edit | edit source]

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