Define one Atomic Mass Unit (a.m.u.)



According to Dalton, each element had a characteristic mass called atomic mass

It is denoted by amu (atomic mass unit) or simply u


The SI unit of atomic mass is u (unified mass)


One atomic mass unit (1u) is a mass unit equal to exactly one-twelfth (1/12th) the mass of one atom of carbon-12 isotope.

1u = 1/12th mass of an Carbon-12 isotope = 1.67377 x 10 -27 kilogram

  1. Class 9
  2. Chapter 3 Class 9 - Atoms And Molecules (Term 2)

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo