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The most stable radioactive isotopes are technetium-97 with a half-life of 4.21 ± 0.16 million years and technetium-98 with 4.2 ± 0.3 million years; current measurements of their half-lives give overlapping confidence intervals corresponding to one standard deviation and therefore do not allow a definite assignment of technetium's most stable ...
[2] [3] Technetium and promethium (atomic numbers 43 and 61, respectively [a]) and all the elements with an atomic number over 82 only have isotopes that are known to decompose through radioactive decay. No undiscovered elements are expected to be stable; therefore, lead is considered the heaviest stable element.
A technetium star, or more properly a Tc-rich star, is a star whose stellar spectrum contains absorption lines of the radioactive metal technetium.The most stable isotope of technetium is 97 Tc with a half-life of 4.21 million years: too short a time to last for the age of the Earth (about 4.5 billion years).
Technetium (43 Tc) is one of the two elements with Z < 83 that have no stable isotopes; the other such element is promethium. [2] It is primarily artificial, with only trace quantities existing in nature produced by spontaneous fission (there are an estimated 2.5 × 10 −13 grams of 99 Tc per gram of pitchblende) [3] or neutron capture by molybdenum.
Electrons per shell: 2, 8, 18, 23, 8, 2 ... followed in the periodic table by elements with stable forms, the other being technetium. ... in the spectrum of the star ...
With the longest-lived isotope of technetium, 97 Tc, having a 4.21-million-year half-life, [10] no technetium remains from the formation of the Earth. [ 11 ] [ 12 ] Only minute traces of technetium occur naturally in Earth's crust—as a product of spontaneous fission of 238 U, or from neutron capture in molybdenum —but technetium is present ...
The half-lives of nuclei also decrease when there is a lopsided neutron–proton ratio, such that the resulting nuclei have too few or too many neutrons to be stable. [ 14 ] The stability of a nucleus is determined by its binding energy , higher binding energy conferring greater stability.
This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour. This represents isotopes of the first 105 elements, except for elements 87 (), 102 and 104 (rutherfordium).