Atoms are incredibly tiny, so weighing them in grams or kilograms is impractical. Instead, scientists use a relative scale called the Atomic Mass Unit (amu), which is now officially written simply as 'u' (unified mass).
Symbol: amu (older) or u (modern 'unified mass').
Definition: 1/12th the mass of a Carbon-12 atom.
Standard Reference: Carbon-12 isotope.
1 amu = 1.66 × 10⁻²⁴ g.
Mass of a proton or neutron ≈ 1 amu.
One Atomic Mass Unit (1 amu) is defined as a mass exactly equal to one-twelfth (1/12th) of the mass of one Carbon-12 atom.
Why Carbon-12? Because it is abundant, stable, and has exactly 6 protons and 6 neutrons. It was chosen as the international standard reference in 1961.
Think of a Carbon-12 atom as a pie cut into exactly 12 equal slices.
If you convert 1 amu into standard metric units, the number is unimaginably small: 1 amu = 1.660539 × 10⁻²⁴ grams
One atomic mass unit (amu or u) is defined as a mass exactly equal to 1/12th of the mass of one Carbon-12 atom.
The Carbon-12 isotope is used as the international standard reference for atomic mass.
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