atomic number


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Related to atomic number: Isotopes, atomic weight

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 ?
It was established in 1913, in full conformity with the hypothesis of Van den Brook, that the atomic numbers of the chemical elements directly reflect the nuclear charge of their atoms.
The next evening, I decided to read and memorize the atomic numbers, too.
For higher atomic numbers, the La line is the automatic first choice until the M[alpha] line becomes available at Z = 70 (for lower atomic numbers the M[alpha] line suffers from anomalous absorption and cannot be used for quantitative analysis).
Decay of the heavier isotope eventually produces dubnium (atomic number 105), whereas the lighter isotope decays down to roentgenium (111).
In an effort to detect any possible effect due solely to atomic weight, as opposed to atomic number, we performed low uncertainty measurements of absorbed current in samples in which the only difference was mass, that is the number of neutrons.
A problem with conventional CT is the occurence of false density readings in plastics where a dopant has a higher atomic number that the host material.
After all, Fermi had been bombarding elements with neutrons to produce elements higher by one atomic number (see 1934).
nanotomografickEi station will be particularly suitable for studying the structures of lighter materials (less atomic number z), typical of all types of polymeric materials based on thermoplastics and thermoplastic elastomers, and mixtures thereof, as well as composites and nanocomposites, but also certain powdered ceramic materials bonded with a polymer matrix.
Elements are arranged according to their increasing atomic numbers. Hydrogen (H), for example, has an atomic number of 1 and is the lightest known natural element on Earth.
convert the atomic numbers of elements into verbal names by replacing each digit of the atomic number with a literal particle, as follows: 0 = nil 1 = un 2 = bi 3 = tri 4 = quad 5 = pent 6 = hex 7 = sept 8 = oct 9 = enn
According to Casey Lisse of the Deep Impact team, copper was chosen because its density put a lot of mass into a small package, its relative softness reduced bounce at impact, and its large atomic number and density contrast with those of elements that were expected to spew from the comet at impact (see p.
In fact, the bombardment of uranium (element number 92) with neutrons might somehow result in the emission by uranium of two alpha particles, which would reduce the atomic number by four and so produce an isotope of radium (element number 88).