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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). Therefore, the detection in 1952 ...
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.
Promethium is the only lanthanide and one of only two elements among the first 82 with no stable or long-lived isotopes. This is a result of a rarely occurring effect of the liquid drop model and stabilities of neighbor element isotopes; it is also the least stable element of the first 84. [4]
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
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).
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.