كتلة ذرية: الفرق بين النسختين

كما يمكن تعيين [[الكتلة المولية ]] لمركب ما عن طريق جمع المتل الذرية النسبية لجميع العناصر المكونة للمركب الكيميائي كما تعطيه [[صيغة كيميائية|صيغته الكيميائية]].

الكتلة الجزيئية لملح الطعام ([[ كلوريد الصوديوم]]):

. For example, the [[standardكتلة atomicذرية weightقياسية]] of [[ironحديد]] is 55.847 g/mol, and therefore one mole of iron as commonly found on earth has a mass of 55.847 grams. The ''atomic mass'' of the ⁵⁶Fe isotope is 55.935 u and one mole of ⁵⁶Fe atoms would then in theory have a mass of 55.935 g, but such amounts of pure ⁵⁶Fe have never been found (or separated out) on Earth. However, there are 22 [[mononuclidicعنصر elementأحادي النويدة]]s of which essentially only a single isotope is found in nature (common examples are fluorine, sodium, aluminum and phosphorus) and for these elements the [[standardكتلة atomicذرية weightقياسية]] and atomic mass are the same. Samples of these elements therefore may serve as reference standards for certain atomic mass values.