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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.
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]
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.
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 ...
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.
Here [Ne] refers to the core electrons which are the same as for the element neon (Ne), the last noble gas before phosphorus in the periodic table. The valence electrons (here 3s 2 3p 3) are written explicitly for all atoms. Electron configurations of elements beyond hassium (element 108) have never been measured; predictions are used below.
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 ...