atomic number

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number

 [num´ber]
a symbol, as a figure or word, expressive of a certain value or a specified quantity determined by count.
atomic number (Z) a number expressive of the number of protons in an atomic nucleus, or the positive charge of the nucleus expressed in terms of the electronic charge.
Avogadro's number (N) (NA) the number of molecules in one mole of a substance: 6.023 × 1023. Called also Avogadro's constant.
CT number the density assigned to a voxel in a CAT scan on an arbitrary scale on which air has a density −1000; water, 0; and compact bone +1000. See also hounsfield unit.
mass number (A) the number of nucleons (protons plus neutrons) in the atom of a nuclide; generally indicated by a superscript preceding the symbol of a chemical element (e.g., 131I), denoting a specific isotope.
oxidation number a number assigned to each atom in a molecule or ion that represents the number of electrons theoretically gained (positive oxidation numbers) or lost (negative numbers) in converting the atom to the elemental form.

a·tom·ic num·ber (Z),

the number of protons in the nucleus of an atom; it indicates the position of the element in the periodic system.

a·tom·ic num·ber

(Z) (ă-tom'ik nŭm'bĕr)
The number of protons in the nucleus of an atom; it indicates the position of the element in the periodic system.
References in periodicals archive ?
Hanagodimath, "Studies on effective atomic numbers and electron densities of some chemical explosives in the energy range 1KeV-100 GeV," Journal of Chemical and Pharmaceutical Research, vol.
Hydrogen has one proton and has been assigned the atomic number 1.
To date, to the best of our knowledge, no report has been published on dopant concentration, effective atomic number, and a TL study of copper-doped potassium borate glasses.
Therefore, we have calculated the mass attenuation coefficients, [mu]/[rho], half-value layer, HVL, tenth-value layer, TVL, effective atomic numbers, [Z.sub.PIeff], and effective electron densities, [N.sub.e, eff], of borate glass samples containing PbO and NiO given in Table 1.
Those elements may combine with the element boron (a metalloid chemical element with atomic number 5 and the chemical symbol B).
Most of the rare earths consist of the elements between the lanthanum (atomic number 57) and lutetium (atomic number 71), with two outliers: scandium (atomic number 21) and yttrium (atomic number 39).
As atomic number gets higher and higher, stability generally diminishes, eventually reaching a point where the new atoms decay away into something else almost as fast as physicists can make them.
It is shown that the atomic number Z is prime at the beginning of the each [s.sup.1], [p.sup.1], [d.sup.1], and f1 energy levels of electrons, with some fluctuation in the actinide and lanthanide series.
For elements of atomic number less than approximately 30, the K[alpha] line is nearly always the best (or only) choice.
The electron microscope used backscatter electrons that are extremely sensitive to the atomic numbers of elements, Ustohal said.
Most ED-XRF analyzers typically measure around 80 elements from atomic numbers as low as sodium (atomic number 11) or magnesium (12) to as high as uranium (92).
Four elements between 1 and 92 now remained to be discovered, atomic numbers 43, 61, 85, and 87.