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Nominal mass is a term used in high level mass spectrometric discussions, it can be calculated using the mass number of the most abundant isotope of each atom, without regard for the mass defect. For example, when calculating the nominal mass of a molecule of nitrogen (N 2) and ethylene (C 2 H 4) it comes out as. N 2 (2*14)= 28 Da C 2 H 4
Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.
The exact mass of an isotopic species (more appropriately, the calculated exact mass [9]) is obtained by summing the masses of the individual isotopes of the molecule. For example, the exact mass of water containing two hydrogen-1 (1 H) and one oxygen-16 (16 O) is 1.0078 + 1.0078 + 15.9949 = 18.0105 Da.
The term isotopes (originally also isotopic elements, [4] now sometimes isotopic nuclides [5]) is intended to imply comparison (like synonyms or isomers). For example, the nuclides 12 6 C, 13 6 C, 14 6 C are isotopes (nuclides with the same atomic number but different mass numbers [6]), but 40 18 Ar, 40 19 K, 40 20 Ca
A chart or table of nuclides maps the nuclear, or radioactive, behavior of nuclides, as it distinguishes the isotopes of an element.It contrasts with a periodic table, which only maps their chemical behavior, since isotopes (nuclides that are variants of the same element) do not differ chemically to any significant degree, with the exception of hydrogen.
Samples must be introduced to the mass spectrometer as pure gases, achieved through combustion, gas chromatographic feeds, [6] or chemical trapping. By comparing the detected isotopic ratios to a measured standard, an accurate determination of the isotopic make up of the sample is obtained. For example, carbon isotope ratios are measured ...
This is an extended version of the energy density table from the main Energy density page: ... Energy density by mass (MJ/kg) Energy density by volume (MJ/L)
Example: the pie chart for boron shows it to be composed of about 20% 10 B and 80% 11 B. This isotope mix causes the atomic weight of ordinary Earthly boron samples to be expected to fall within the interval 10.806 to 10.821. and this interval is the standard atomic weight. Boron samples from unusual sources, particularly non-terrestrial ...