:18 1 u has a value of 1.660 539 066 60(50) × 10 −27 kg. Its symbol is 'u'. n. Abbr. The average mass of all the isotopes of an element. atomic mass unit. (c) It means that one atom of oxygen is 16 times heavier than 1/12 of a C-12 atom. It is equal to the sum of the atomic masses of all the atoms present in one molecule of the substance.e.g. 1 AMU = 1.67377 x 10 -27 kilogram or 1.67377 x 10 -24 gram. Define atomic mass unit. See more. However, because each atom has a very small mass, this is not very helpful. 1 atomic mass unit is defined as 1/12 of the mass of a single carbon-12 atom. (b) The atomic mass of an element is the relative mass of its atom as compared with the mass of a carbon-12 atom taken as 12 units. 1 AMU = Average of the proton rest mass and the neutron rest mass. Atomic mass unit definition is - a unit of mass for expressing masses of atoms, molecules, or nuclear particles equal to 1/12 the mass of a single atom of the most abundant carbon isotope 12C —called also dalton. The atomic unit mass is symbolized as AMU or amu. (d) Relative Formula Mass :- Molecular mass of NH3= Atomic mass of N + 3 x Atomic mass of H = 14 + 3 x 1 Q12 : Calculate the formula unit masses of ZnO, Na2O, K2CO3, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u. Number of protons in an atom. atomic number. Atomic mass can be expressed in grams. The protons and neutrons of the nucleus account for nearly all of the total mass of atoms, with the electrons … Instead, atomic mass is expressed in unified atomic mass units (unit symbol: u). (a) One atomic mass unit is defined as exactly one-twelfth the mass of an atom of carbon-12. isotopes. In chemistry, an atomic mass unit or AMU is a physical constant equal to one-twelfth of the mass of an unbound atom of carbon-12.It is a unit of mass used to express atomic masses and molecular masses.When the mass is expressed in AMU, it roughly reflects the sum of the number of protons and neutrons in the atomic nucleus (electrons have so much less mass … atomic mass unit synonyms, atomic mass unit pronunciation, atomic mass unit translation, English dictionary definition of atomic mass unit. The molecular mass of substance is the relative mass of its molecule expressed in atomic mass unit(u). amu A unit of mass equal to 1/12 the mass of the most abundant isotope of carbon, carbon-12, which is assigned a mass of 12. neutrons. one molecule of water (H 2 O) contains two atoms of hydrogen and one atom of oxygen. A unit of mass that describes the mass of an atom or molecule. Atomic weight, also called relative atomic mass, ratio of the average mass of a chemical element’s atoms to some standard. Atomic mass unit definition, a unit of mass, equal to 1/12 (0.0833) the mass of the carbon-12 atom and used to express the mass of atomic and subatomic particles. An atomic unit of mass is defined as accurately 1/12 the mass of a carbon-12 atom. Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12.An isotope is one of two or more species of atoms of the same chemical element that have different atomic mass numbers (protons + … The carbon-12 atom has six neutrons and six protons in its nucleus. 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