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The longest-lived of these isotopes, and the most relevantly studied, are 90 Sr with a half-life of 28.9 years, 85 Sr with a half-life of 64.853 days, and 89 Sr (89 Sr) with a half-life of 50.57 days. All other strontium isotopes have half-lives shorter than 50 days, most under 100 minutes.
Rubidium (37 Rb) has 36 isotopes, with naturally occurring rubidium being composed of just two isotopes; 85 Rb (72.2%) and the radioactive 87 Rb (27.8%). 87 Rb has a half-life of 4.92 × 1010 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread. 87 Rb has been used extensively in dating rocks; 87 Rb decays ...
Isotopes of antimony (51Sb) Antimony (51 Sb) occurs in two stable isotopes, 121 Sb and 123 Sb. There are 37 artificial radioactive isotopes, the longest-lived of which are 125 Sb, with a half-life of 2.75856 years; 124 Sb, with a half-life of 60.2 days; and 126 Sb, with a half-life of 12.35 days. All other isotopes have half-lives less than 4 ...
edit. Potassium (. 19K) has 25 known isotopes from 34. K to 57. K as well as 31. K, as well as an unconfirmed report of 59. K. [3] Three of those isotopes occur naturally: the two stable forms 39. K (93.3%) and 41. K (6.7%), and a very long-lived radioisotope 40.
Naturally occurring dysprosium (66 Dy) is composed of 7 stable isotopes, 156 Dy, 158 Dy, 160 Dy, 161 Dy, 162 Dy, 163 Dy and 164 Dy, with 164 Dy being the most abundant (28.18% natural abundance). Twenty-nine radioisotopes have been characterized, with the most stable being 154 Dy with a half-life of 1.4 million years, 159 Dy with a half-life of ...
Radium (88 Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given. The longest lived, and most common, isotope of radium is 226 Ra with a half-life of 1600 years. 226 Ra occurs in the decay chain of 238 U (often referred to as the radium series). Radium has 34 known isotopes from 201 Ra to 234 Ra.
A simple fraction (also known as a common fraction or vulgar fraction, where vulgar is Latin for "common") is a rational number written as a / b or , where a and b are both integers. [9] As with other fractions, the denominator (b) cannot be zero. Examples include 1 2 , − 8 5 , −8 5 , and 8 −5 .
Isotopes of technetium. 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 ...