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  2. Standard atomic weight - Wikipedia

    en.wikipedia.org/wiki/Standard_atomic_weight

    IUPAC publishes one formal value for each stable chemical element, called the standard atomic weight. [17] [1]: Table 1 Any updates are published biannually (in uneven years). In 2015, the atomic weight of ytterbium was updated. [17] Per 2017, 14 atomic weights were changed, including argon changing from single number to interval value. [18] [19]

  3. Mass number - Wikipedia

    en.wikipedia.org/wiki/Mass_number

    The atomic weight is a mass ratio, while the mass number is a counted number (and so an integer). This weighted average can be quite different from the near-integer values for individual isotopic masses. For instance, there are two main isotopes of chlorine: chlorine-35 and chlorine-37. In any given sample of chlorine that has not been ...

  4. Atomic mass - Wikipedia

    en.wikipedia.org/wiki/Atomic_mass

    The atomic mass or relative isotopic mass are sometimes confused, or incorrectly used, as synonyms of relative atomic mass (also known as atomic weight) or the standard atomic weight (a particular variety of atomic weight, in the sense that it is standardized). However, as noted in the introduction, atomic mass is an absolute mass while all ...

  5. List of equations in nuclear and particle physics - Wikipedia

    en.wikipedia.org/wiki/List_of_equations_in...

    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

  6. Relative atomic mass - Wikipedia

    en.wikipedia.org/wiki/Relative_atomic_mass

    The prevailing IUPAC definitions (as taken from the "Gold Book") are: atomic weight – See: relative atomic mass [11] and relative atomic mass (atomic weight) – The ratio of the average mass of the atom to the unified atomic mass unit. [12] Here the "unified atomic mass unit" refers to 1/12 of the mass of an atom of 12 C in its ground state ...

  7. Molar mass - Wikipedia

    en.wikipedia.org/wiki/Molar_mass

    The molar mass of atoms of an element is given by the relative atomic mass of the element multiplied by the molar mass constant, M u ≈ 1.000 000 × 10 −3 kg/mol ≈ 1 g/mol. For normal samples from Earth with typical isotope composition, the atomic weight can be approximated by the standard atomic weight [2] or the conventional atomic weight.

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  9. Commission on Isotopic Abundances and Atomic Weights

    en.wikipedia.org/wiki/Commission_on_Isotopic...

    With the discovery of oxygen isotopes in 1929, a situation arose where chemists based their calculations on the average atomic mass (atomic weight) of oxygen whereas physicists used the mass of the predominant isotope of oxygen, oxygen-16. This discrepancy became undesired and a unification between the chemistry and physics was necessary. [13]