mass number

number /num·ber/ (num´ber) a symbol, as a figure or word, expressive of a certain value or a specified quantity determined by count.

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atomic number  (Z ) a number expressive of the number of protons in an atomic nucleus.

Avogadro's number  (N ) (N A) the number of molecules in one mole of a substance: 6.023 × 1023.

mass number  (A ) the number expressive of the mass of a nucleus, being the total number of protons and neutrons in the nucleus of an atom or nuclide.

oxidation number  a number assigned to each atom in a molecule or ion that represents the number of electrons theoretically lost (negative numbers) or gained (positive numbers) in converting the atom to the elemental form (which has an oxidation number of zero). The sum of the oxidation numbers for all atoms in a neutral compound is zero; for polyatomic ions, it is equal to the ionic charge.

tooth number  a number assigned for each of the permanent teeth in consecutive order, with 1 for the upper right third molar and 17 for the lower left third molar, and proceeding around each jaw.

turnover number  the number of molecules of substrate acted upon by one molecule of enzyme per minute.

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mass number (A),

the sum of the number of protons and neutrons in the nucleus of an atom or isotope. See also 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) (N_A) 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.

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mass number,

n the total number of protons and neutrons within the nucleus of an atom. This number represents the atom's approximate mass.

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mass number (A),

n the number of nucleons (protons and neutrons) in the nucleus of an atom.

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mass

1. a lump or collection of cohering particles.

2. that characteristic of matter which gives it inertia.

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mass-action ratios

the ratio of substrate to product, where the predominance of one, usually the substrate, over the other thermodynamically favors a particular direction for a reaction.

inner cell mass

an internal cluster of cells at the embryonic pole of the blastocyst which develops into the body of the embryo.

lean body mass

that part of the body including all its components except neutral storage lipid; in essence, the fat-free mass of the body.

mass medication

(or immunization, or treatment, or prophylaxis, or testing, or screening) application of the procedure to all of the animals in the population, which may be as small as a herd or as large as a national herd. This sort of strategy has been used extensively and for many years in the control of diseases of animals, and has been the principal reason for the dramatic virtual eradication of the major plagues in many countries. The unintelligent extension of the strategy to the control of wastage caused by endemic disease has contributed most to the problem of residues of antibacterial drugs in the human food chain. See also mass medication.

mass number

the number used to express the mass of a nucleus, being the total number of nucleons, protons and neutrons in the nucleus of an atom or nuclide; symbol A.

mass reflex

reflex actions by all the body parts controlled by the part of the spinal cord which has been injured.

thalamic intermediate mass

see interthalamic adhesion.

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number

a symbol, as a figure or word, expressive of a certain value or a specified quantity determined by count.

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atomic number

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; symbol A.

Avogadro's number

see avogadro's number.

mass number

see mass number.

Reynold's number

see reynold's number.