What measures atomic weight?
Atomic weight is the ratio of the average atomic mass of an element (always taken from some sample source) to 1/12th of the mass of an atom of carbon-12. Molecular mass or molecular weight is the mass of a molecule. It is calculated as the sum of the mass of each constituent atom multiplied by the number of atoms of that element in the molecular formula. The molecular mass of small to medium size molecules, measured by mass spectrometry, determines stoichiometry. Atomic weight is the ratio of the average atomic mass of an element (always taken from some sample source) to 1/12th of the mass of an atom of carbon-12. It is, more or less, a conventional way of referring to the standard atomic weights published by IUPAC (International Union of Pure and Applied Chemistry). Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12. An isotope is one of two or more species of atoms of the same chemical element that have different atomic mass numbers (protons + neutrons). Atomic weight, ratio of the average mass of a chemical element’s atoms to some standard. Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12. The standard atomic weight is the average mass of an element in atomic mass units. One atomic mass unit, or amu, is equal to 1/12 the mass of a single carbon-12 atom. (To put that in perspective, a single carbon atom is roughly equal to 5.857 × 10^-26 ounces.). Say that we want to calculate the molecular weight of water. The molecular weight is the sum of the atomic weights of the atoms in the molecule. We can go about our calculation by making a table. We list the atoms in the molecule down the left. H. Steffen Peiser Edward Wichers. Atomic weight, ratio of the average mass of a chemical element’s atoms to some standard. Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12. Atomic mass is measured in a unit called an atomic mass unit. This unit is defined as 1/12 of the mass of a carbon-12 atom at ground state. An atomic mass unit is approximately 1.66053886 x 10-27 kg. Atomic mass is measured in atomic mass units (amu) and Daltons. It is commonly expressed in unified atomic mass units (u) where by international agreement, 1 unified atomic mass unit is defined as 1/12 of the mass of a single carbon-12 atom (at rest).
The standard atomic weight is the average mass of an element in atomic mass units. One atomic mass unit, or amu, is equal to 1/12 the mass of a single carbon-12 atom.