Define one atomic mass unit (a.m.u.).

An atomic mass unit is defined as 1/12^th the mass of a carbon-12 atom. It is a unit of mass that is used to represent the atomic masses of elements.

• Elements are the simplest substances of matter that cannot be chemically reduced any further.
• It is difficult to measure the mass of individual atoms as they are so small that the metric ‘grams’ is not practical to use.
• The mass of one atom of C-12 is 1.99×10⁻²³g.
• Atomic physicists and chemists, therefore, assumed the unified atomic mass unit (AMU) to describe the atomic masses on the basis of their subatomic particles.
• The atomic mass unit is also expressed as a.m.u or u (unified).
• A carbon-12 atom comprises 6 neutrons and 6 protons.
• 1 amu can be understood as the average of the proton and neutron rest mass.
• We can represent 1 a.m.u. = 1.67377 x 10^-27 kilogram or 1.67377 x 10^-24 gram.

The unified atomic mass unit is a unit describing the mass of a neutral carbon-12 isotope at rest. Every proton and neutron weighs approximately 1 AMU.

---

Also Check: