Two
nuclide
A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state.
The word ''nuclide'' was coined by Truman ...
s are isotones if they have the same
neutron number
The neutron number, symbol ''N'', is the number of neutrons in a nuclide.
Atomic number (proton number) plus neutron number equals mass number: . The difference between the neutron number and the atomic number is known as the neutron excess: . ...
''N'', but different
proton number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
''Z''. For example,
boron-12 and
carbon-13
Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons. As one of the environmental isotopes, it makes up about 1.1% of all natural carbon on Earth.
Detection by mass spectrometry
A mass ...
nuclei both contain 7
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s, and so are isotones. Similarly,
36S,
37Cl,
38Ar,
39K, and
40Ca nuclei are all isotones of 20 because they all contain 20 neutrons. Despite its similarity to the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
for "same stretching", the term was formed by the German physicist
K. Guggenheimer by changing the "p" in "
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
" from "p" for "proton" to "n" for "neutron".
The largest numbers of
observationally stable
Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes.
Th ...
nuclides exist for isotones 50 (five:
86Kr,
88Sr,
89Y,
90Zr,
92Mo) and 82 (six:
138Ba,
139La,
140Ce,
141Pr,
142Nd,
144Sm).
Neutron number
The neutron number, symbol ''N'', is the number of neutrons in a nuclide.
Atomic number (proton number) plus neutron number equals mass number: . The difference between the neutron number and the atomic number is known as the neutron excess: . ...
s for which there are no stable isotones are 19, 21, 35, 39, 45, 61, 89, 115, 123, and 127 or more. In contrast, the
proton number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
s for which there are no stable isotopes are
43,
61, and
83 or more.
[via :File:NuclideMap_stitched.png; note also ]Isotopes of bismuth
Bismuth (83Bi) has 41 known isotopes, ranging from 184Bi to 224Bi. Bismuth has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as . Although bismuth-209 is now known to be unstable, it ...
This is related to nuclear
magic numbers, the number of
nucleon
In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number (nucleon number).
Until the 1960s, nucleons were ...
s forming complete
shells within the nucleus, e.g. 2, 8, 20, 28, 50, 82, and 126. No more than one stable nuclide has the same odd neutron number, except for 1 (
2H and
3He), 5 (
9Be and
10B), 7 (
13C and
14N), 55 (
97Mo and
99Ru), and 107 (
179Hf and
180mTa). Odd neutron numbers for which there is a stable nuclide and a
primordial radionuclide
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...
are 27 (
50V), 65 (
113Cd), 81 (
138La), 85 (
147Sm), and 105 (
176Lu). Neutron numbers for which there are two primordial radionuclides are 88 (
151Eu and
152Gd) and 112 (
187Re and
190Pt).
See also
*
Isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
s are nuclides having the same number of
protons
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
: e.g. carbon-12 and carbon-13.
*
Isobars are nuclides having the same
mass number
The mass number (symbol ''A'', from the German word ''Atomgewicht'' tomic weight, also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approxima ...
(i.e. sum of protons plus neutrons): e.g. carbon-12 and boron-12.
*
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state, higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited ...
s are different excited states of the same type of nucleus. A transition from one isomer to another is accompanied by emission or absorption of a
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
, or the process of
internal conversion
Internal conversion is a non-radioactive, atomic decay process where an excited nucleus interacts electromagnetically with one of the orbital electrons of an atom. This causes the electron to be emitted (ejected) from the atom. Thus, in internal ...
. (Not to be confused with
chemical isomers.)
Notes
{{Authority control
Nuclear physics