atomic number (redirected from Proton 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.

---

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.

---

atomic number

n. Abbr. at. no., at no

The number of protons in an atomic nucleus; it indicates the position of an element in the periodic table.

---

atomic number,

the number of protons in the nucleus of an atom of a particular element. In a neutral atom, the atomic number equals the number of electrons. See also atom, electron, proton.

---

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.

---

atomic number,

n the number of protons within an atom's nucleus.

---

atomic (tom´ik),

adj pertaining to the atom.

atomic energy,

n See energy, atomic.

atomic mass number,

n (symbol: A), the total number of nucleons (protons and neutrons) of which an atom is composed.

atomic number (Z),

n 1. the number of electrons outside the nucleus of a neutral atom.
n 2. the number of protons in the nucleus.

atomic structure theory,

n the theory that matter is composed of a vast number of particles, or atoms, bound together by a force of attraction of electrical charges.

atomic weight,

n the weight of one atom of an element as compared with the weight of an atom of hydrogen.

---

number

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

---

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.