formula weight

The atomic mass (ma) is the mass of an atom at rest, most often expressed in unified atomic mass units. The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom (when the atom is motionless). The atomic mass is sometimes incorrectly used as a synonym of relative atomic mass, average atomic mass and atomic weight; however, these differ subtly from the atomic mass. The atomic mass is defined as the mass of an atom, which can only be one isotope at a time and is not an abundance-weighted average. The actual numerical difference is usually very small such that it does not affect most bulk calculations but such an error can be critical when considering individual atoms.
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The molecular mass (abbreviated Mr) of a substance, formerly also called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). This is distinct from the relative molecular mass of a molecule, which is the ratio of the mass of that molecule to 1/12 of the mass of carbon 12 and is a dimensionless number. Relative molecular mass is abbreviated to Mr.
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Compare with molecular weight and empirical formula .The formula weight is the sum of the atomic weights of the atoms in an empirical formula . Formula weights are usually written in atomic mass units (u).

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Eng: formula weight
Urdu: کِسی مادّے کا سلامی وزن جو گرام میں ظاہِر کیا گیا ہو ۔