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Yttrium isotopes with mass numbers at or above 90 decay mainly by electron emission (neutron → proton) to form zirconium (Z = 40) isotopes. [30] Isotopes with mass numbers at or above 97 are also known to have minor decay paths of β − delayed neutron emission .
Natural yttrium (39 Y) is composed of a single isotope yttrium-89. The most stable radioisotopes are 88 Y, which has a half-life of 106.6 days, and 91 Y, with a half-life of 58.51 days. All the other isotopes have half-lives of less than a day, except 87 Y, which has a half-life of 79.8 hours, and 90 Y, with 64 hours.
Isotones are nuclides with the same number of neutrons but differing numbers of protons. Isotones neighbor each other horizontally. Examples include carbon-14, nitrogen-15, and oxygen-16 in the table above. Isobars are nuclides with the same number of nucleons (i.e. mass number) but different numbers of protons and neutrons. Isobars neighbor ...
As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus; if too many or too few neutrons are present with regard to the optimum ratio, the nucleus becomes unstable and subject to certain types of nuclear decay.
The isobar forming 132 Te/ 132 I is: Tin-132 (half-life 40 s) decaying to antimony-132 (half-life 2.8 minutes) decaying to tellurium-132 (half-life 3.2 days) decaying to iodine-132 (half-life 2.3 hours) which decays to stable xenon-132. The creation of tellurium-126 is delayed by the long half-life (230 k years) of tin-126.
The neutron number (symbol N) is the number of neutrons in a nuclide. Atomic number (proton number) plus neutron number equals mass number : Z + N = A . The difference between the neutron number and the atomic number is known as the neutron excess: D = N − Z = A − 2 Z .
The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number. For example, carbon-12 , carbon-13 , and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively.
In addition to the four stable isotopes, thirty-two unstable isotopes of strontium are known to exist, ranging from 73 Sr to 108 Sr. Radioactive isotopes of strontium primarily decay into the neighbouring elements yttrium (89 Sr and heavier isotopes, via beta minus decay) and rubidium (85 Sr, 83 Sr and lighter isotopes, via positron emission or ...