= Dalton
{disambiguate=unit}
{title2=$\mathrm{Da}=\mathrm u$}
{wiki}
= Unified atomic mass unit
{synonym}
The <unified atomic mass unit> and <dalton (unit)> are names for the same <mass> unit:
$$
1\,\mathrm u=1\,\mathrm{Da}=\frac{m_{\rm a}({}^{12}\mathrm C)}{12},
$$
where the <carbon-12> <chemical atom> is free, at rest, and in its nuclear and electronic <ground state>. Its conversion to <SI> <mass> units is determined experimentally. See <The International System of Units (SI), ninth edition, SI Brochure> (Table 8, footnote (f), printed p. 146: dalton and unified atomic mass unit).
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