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Atomic Mass Unit (amu)

1 amu = 1 u = 1.66054 × 10⁻²⁷ kg
Quick Reference
Formula / Notation1 amu = 1 u = 1.66054 × 10⁻²⁷ kg
Also Known Asamu; u (unified atomic mass unit); Dalton (Da); atomic mass unit; 1/12 of ¹²C mass

What is Atomic Mass Unit (amu)?

The atomic mass unit (amu, also written as u or Da for Dalton) is the standard unit of mass used to express the mass of atoms and molecules. It is defined as exactly 1/12 of the mass of a carbon-12 atom (¹²C). One amu is approximately equal to 1.66054 × 10⁻²⁷ kg.

Formula & Notation

1 amu = 1 u = 1.66054 × 10⁻²⁷ kg

Other Names / Synonyms: amu; u (unified atomic mass unit); Dalton (Da); atomic mass unit; 1/12 of ¹²C mass

Properties & Characteristics

1 amu = 1/12 mass of ¹²C = 1.66054 × 10⁻²⁷ kg; proton mass ≈ 1.0073 amu; neutron mass ≈ 1.0087 amu; electron mass ≈ 0.000549 amu; 1 mol of amu = 1 g (Avogadro's number connection); also called unified atomic mass unit (u) or Dalton (Da)

Uses & Applications

Expressing atomic and molecular masses; mass spectrometry (m/z values); nuclear physics; protein and polymer molecular weight characterisation (Da, kDa); chemistry calculations and stoichiometry

Safety Information

No hazard — a unit of measurement.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Atomic Mass Unit (amu)
Formula 1 amu = 1 u = 1.66054 × 10⁻²⁷ kg
Synonyms amu; u (unified atomic mass unit); Dalton (Da); atomic mass unit; 1/12 of ¹²C mass

Frequently Asked Questions

The atomic mass unit (amu, also written as u or Da for Dalton) is the standard unit of mass used to express the mass of atoms and molecules. It is defined as exactly 1/12 of the mass of a carbon-12 atom (¹²C). One amu is approximately equal to 1.66054 × 10⁻²⁷ kg.

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