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The IUPAC definition [1] of relative atomic mass is: An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of an atom of 12 C. The definition deliberately specifies "An atomic weight ...", as an element will have different relative atomic masses ...
Definition Name Symbol relative atomic mass: A r: Ratio of the average mass per atom of an element to 1/12 of the mass of an atom of the nuclide 12 C one 1 Formerly called atomic/molecular weight. Example: A r (Cl) = 35.453. Both quantities depend on the nuclidic composition. relative molecular mass: M r
Quantity (common name/s) (Common) symbol/s Defining equation SI units Dimension Number of atoms N = Number of atoms remaining at time t. N 0 = Initial number of atoms at time t = 0
Atomic mass: (applies to each element) the average mass of the atoms of an element, in daltons (Da), a.k.a. atomic mass units (amu). Atomic number: (applies to individual atoms or pure elements) the number of protons in each nucleus; Relative atomic mass, a.k.a. atomic weight: (applies to individual isotopes or specific mixtures of isotopes of ...
Thus, the atomic mass of a carbon-12 atom is 12 Da by definition, but the relative isotopic mass of a carbon-12 atom is simply 12. The sum of relative isotopic masses of all atoms in a molecule is the relative molecular mass. The atomic mass of an isotope and the relative isotopic mass refers to a certain specific isotope of an element.
The molar mass constant, usually denoted by M u, is a physical constant defined as one twelfth of the molar mass of carbon-12: M u = M(12 C)/12. [1] The molar mass of an element or compound is its relative atomic mass (atomic weight) or relative molecular mass (molecular weight or formula weight) multiplied by the molar mass constant.
Atomic weight and relative atomic mass are synonyms. The standard atomic weight is a special value of the relative atomic mass. It is defined as the "recommended values" of relative atomic masses of sources in the local environment of the Earth's crust and atmosphere as determined by the IUPAC Commission on Atomic Weights and Isotopic ...
Quantity (Common Name/s) (Common) Symbol/s Defining Equation SI Units Dimension Relative atomic mass of an element : A r, A, m ram = /The average mass is the average of the T masses m i (X) corresponding the T isotopes of X (i is a dummy index labelling each isotope):