1 Atomic mass units tell the mass of one mole of a given element or molecule in grams. 2  This is a very useful property when it comes to practical calculations, as it allows easy conversion between the mass and moles of a given quantity of atoms or molecules of the same type.
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The relative amounts of each isotope for any element represents the isotope distribution for that element. The atomic weight is the average of the isotope weights weighted for the isotope distribution and expressed on the 12 C scale as mentioned above. For a discussion of the use of weight rather than mass (preferred by physicists), see the discussion in ref. 1. The 1999 values were published in 2001 (ref.
http://www.webelements.com/periodicity/atomic_weight/
For example, the atomic weight of the element chlorine is 35.453, determined by averaging the atomic masses and relative abundances of its two main naturally occurring isotopes, which have atomic masses of about 35 and 37.
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atomic weight - (chemistry) the mass of an atom of a chemical element expressed in atomic mass units. atomic mass, relative atomic mass. mass-the property of a body that causes it to have weight in a gravitational field.
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Standard atomic weights: periodicity. 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 12 C in its nuclear and electronic ground state. (Refs. 1 and 2).
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The average mass of an atom of an element, usually expressed relative to the mass of carbon 12, which is assigned 12 atomic mass units.
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atomic weight. The average mass of a chemical element, expressed in atomic mass units. The atomic weight of an element having more than one principal isotope is calculated both from the atomic masses of the isotopes and from the relative abundance of each isotope in nature.
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1 Our carbon atom has 6 protons + 6 neutrons = 12. 2  The atomic mass of this specific carbon atom is 12. 3  If it was a carbon-13 isotope, on the other hand, we would know that it has 6 protons + 7 neutrons = an atomic weight of 13.
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1 If carbon-12 makes up 99% of the sample and carbon-13 makes up 1% of the sample, multiply 12 (the atomic mass of carbon-12) by 0.99 and 13 (the atomic mass of carbon-13) by 0.01. 2  A reference book will give percent proportions based on all the known amounts of an element's isotopes.
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One atomic mass unit is equal to 1.660538921 × 10 -27 kg, or 1/12th of the mass of a standard carbon-12 isotope. When expressed this way, atomic mass is called relative isotopic mass, which has the same numerical value as atomic mass. However, relative isotopic mass is technically unit-less.
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what unit is the atomic weight of an element in
The atomic weight of an element is in unit mass.