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Isobars are atoms of different chemical elements that have the same number of nucleons. Correspondingly, isobars differ in atomic number (or number of protons) but have the same mass number. An example of a series of isobars is 40 S, 40 Cl, 40 Ar, 40 K, and 40 Ca. While the nuclei of these nuclides all contain 40 nucleons, they contain varying ...
The term isotopes (originally also isotopic elements, [4] now sometimes isotopic nuclides [5]) is intended to imply comparison (like synonyms or isomers). For example, the nuclides 12 6 C, 13 6 C, 14 6 C are isotopes (nuclides with the same atomic number but different mass numbers [6]), but 40 18 Ar, 40 19 K, 40 20 Ca are isobars (nuclides with ...
Isobars neighbor each other diagonally from lower-left to upper-right. Examples include carbon-14, nitrogen-14, and oxygen-14 in the table above. Isodiaphers are nuclides with the same difference between their numbers of neutrons and protons (N − Z). Like isobars, they follow diagonal lines, but at right angles to the isobar lines (from upper ...
As mentioned above, the Mattauch isobar rule cannot make predictions as to the half-lives of the beta-unstable isotopes. Hence there are a few cases where isobars of adjacent elements both occur primordially, as the half-life of the unstable isobar is over a billion years. This occurs for the following mass numbers:
In physics, mirror nuclei are a pair of isobars of two different elements where the number of protons of isobar one (Z 1) equals the number of neutrons of isobar two (N 2) and the number of protons of isotope two (Z 2) equals the number of neutrons in isotope one (N 1); in short: Z 1 = N 2 and Z 2 = N 1.
For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [7] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess, [8] which for 35 Cl is –0.03115.
This remarkable difference of nuclear binding energy between neighbouring nuclei, especially of odd-A isobars, has important consequences: unstable isotopes with a nonoptimal number of neutrons or protons decay by beta decay (including positron decay), electron capture or more exotic means, such as spontaneous fission and cluster decay.
Stable even–even nuclides number as many as three isobars for some mass numbers, and up to seven isotopes for some atomic numbers. Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 ( deuterium ), lithium-6 , boron-10 , nitrogen-14 , and tantalum-180m .