mass number

the total number of neutrons and protons in the nucleus of a particular atom.

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

Mass number

The mass number A of an atom is the total number of its nuclear constituents, or nucleons, as the protons and neutrons are collectively called. The mass number is placed before and above the elemental symbol, thus ²³⁸U. The mass number gives a useful rough figure for the atomic mass; for example, ¹H = 1.00814 atomic mass units (amu), ²³⁸U = 238.124 amu, and so on. See Atomic number

mass number

Symbol: A. The number of protons and neutrons (i.e. nucleons) in the nucleus of a particular atom. It is the number closest to the mass of a nuclide in atomic mass units, i.e. in units equal to 1/12 of the mass of a carbon-12 atom. See also atomic number.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

mass number

[′mas ‚nəm·bər]

(nuclear physics)

The sum of the numbers of protons and neutrons in the nucleus of an atom or nuclide. Also known as nuclear number; nucleon number.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Mass Number

the number of nucleons (protons and neutrons) in the atomic nucleus; designated by the letter A and usually indicated as a superscript to the left of the symbol of an element. The mass number and charge of a nucleus Z, expressed in units of elementary electric charge, determine the composition of the atomic nucleus: Z protons and (A — Z) neutrons. The mass of any atom, expressed in atomic mass units and rounded to the nearest whole number, is equal to its mass number.

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References in periodicals archive

It should be mentioned that the first column of the table refers to the constituent elements of the nuclear emulsion, while the second and third column are related to the mass number and root-mean-square (rms) radius of the corresponding elements.

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The "resistance" of a nucleus can be bond by their coupling energy which shows the energy required for destroying the nucleus into its consisting nucleons (their number in the nucleus is equal to the mass number A expressed in atomic units of mass, a.m.u.).

On the necessity of using element no.155 in the chemical physical calculations: again on the upper limit in the periodic table of elements

The numbers ([M.sub.A], [M.sub.B], [M.sub.N]), determining the cluster and nucleon structures assumed in each system are taken as follows: [M.sub.A] = 1, [M.sub.N] =2 while [M.sub.B] is different for each reaction and it is equal to B/2, where B is the mass number of the target nucleus.

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114, with mass number 289, while scientists suspect nucleus No.

Upper limit of the periodic table and synthesis of superheavy elements

The people claiming they want colorblind admissions aren't likely to welcome mass numbers of Asian American classmates with open arms."

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Residents of the community pulled in mass numbers at the church compound to witness the drama, standing in total surprise as church members divided in two groups between the prophet and the senior pastor used alleged abusive languages that this paper cannot mention.

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Beginning next year, you can be confident your new pet didn't come from a puppy mill--a facility where dogs and other animals are bred in mass numbers, often in inhumane conditions.

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