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Standard atomic weight Ar°(Cr) | ||||||||||||||||||||||||||||||||||||
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Naturally occurring chromium (24Cr) is composed of four stable isotopes; 50Cr, 52Cr, 53Cr, and 54Cr with 52Cr being the most abundant (83.789% natural abundance). Twenty-two radioisotopes, all synthetic, have been characterized, the most stable being 51Cr with a half-life of 27.70 days. All of the remaining radioactive isotopes have half-lives less than a day and for the majority of these less than a minute. This element also has two very short-lived meta states: 45mCr and 59mCr.
53Cr is the radiogenic decay product of 53Mn. Chromium and manganese are found together sufficiently for measurement of both to find application in isotope geology. Mn-Cr isotope ratios reinforce the evidence from 26Al and 107 Pd for the early history of the Solar System. Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites indicate a non-zero initial 53Mn/55Mn ratio, implying that Cr isotopic variation must result from in-situ decay of 53Mn in differentiated planetary bodies. Hence 53Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of the Solar System.
Chromium isotope ratios also allow its abundance in seawater sediments to be used as a proxy for atmospheric oxygen concentrations, as rates of certain leaching reactions exhibit variation. [4]
The known isotopes of chromium range from 42Cr to 70Cr. The primary decay mode before the most abundant stable isotope, 52Cr, is electron capture and the primary mode after is beta decay.
Nuclide [n 1] | Z | N | Isotopic mass (Da) [5] [n 2] [n 3] | Half-life [1] [n 4] | Decay mode [1] [n 5] | Daughter isotope [n 6] | Spin and parity [1] [n 7] [n 4] | Natural abundance (mole fraction) | |||||||||||
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Excitation energy [n 4] | Normal proportion [1] | Range of variation | |||||||||||||||||
42Cr | 24 | 18 | 42.00758(32)# | 13.3(10) ms | β+ (94.4%) | 42V | 0+ | ||||||||||||
β+, p (5.6%) | 41Ti | ||||||||||||||||||
43Cr | 24 | 19 | 42.99789(22)# | 21.1(3) ms | β+, p (79.3%) | 42Ti | (3/2+) | ||||||||||||
β+, 2p (11.6%) | 41Sc | ||||||||||||||||||
β+ (8.97%) | 43V | ||||||||||||||||||
β+, 3p (0.13%) | 40Ca | ||||||||||||||||||
44Cr | 24 | 20 | 43.985591(55) | 42.8(6) ms | β+ (88%) | 44V | 0+ | ||||||||||||
β+, p (12%) | 43Ti | ||||||||||||||||||
45Cr | 24 | 21 | 44.979050(38) | 60.9(4) ms | β+ (65.6%) | 45V | 7/2−# | ||||||||||||
β+, p (34.4%) | 44Ti | ||||||||||||||||||
45mCr [n 8] | 107(1) keV | >80 μs | IT | 45Cr | (3/2) | ||||||||||||||
46Cr | 24 | 22 | 45.968361(12) | 224.3(13) ms | β+ | 46V | 0+ | ||||||||||||
47Cr | 24 | 23 | 46.9628950(56) | 461.6(15) ms | β+ | 47V | 3/2− | ||||||||||||
48Cr | 24 | 24 | 47.9540294(78) | 21.56(3) h | β+ | 48V | 0+ | ||||||||||||
49Cr | 24 | 25 | 48.9513337(24) | 42.3(1) min | β+ | 49V | 5/2− | ||||||||||||
50Cr | 24 | 26 | 49.94604221(10) | Observationally Stable [n 9] | 0+ | 0.04345(13) | |||||||||||||
51Cr | 24 | 27 | 50.94476539(18) | 27.7015(11) d | EC | 51V | 7/2− | ||||||||||||
52Cr | 24 | 28 | 51.94050471(12) | Stable | 0+ | 0.83789(18) | |||||||||||||
53Cr | 24 | 29 | 52.94064630(12) | Stable | 3/2− | 0.09501(17) | |||||||||||||
54Cr | 24 | 30 | 53.93887736(14) | Stable | 0+ | 0.02365(7) | |||||||||||||
55Cr | 24 | 31 | 54.94083664(25) | 3.497(3) min | β− | 55Mn | 3/2− | ||||||||||||
56Cr | 24 | 32 | 55.94064898(62) | 5.94(10) min | β− | 56Mn | 0+ | ||||||||||||
57Cr | 24 | 33 | 56.9436121(20) | 21.1(10) s | β− | 57Mn | (3/2)− | ||||||||||||
58Cr | 24 | 34 | 57.9441845(32) | 7.0(3) s | β− | 58Mn | 0+ | ||||||||||||
59Cr | 24 | 35 | 58.94834543(72) | 1.05(9) s | β− | 59Mn | (1/2−) | ||||||||||||
59mCr | 502.7(11) keV | 96(20) μs | IT | 59Cr | (9/2+) | ||||||||||||||
60Cr | 24 | 36 | 59.9496417(12) | 490(10) ms | β− | 60Mn | 0+ | ||||||||||||
61Cr | 24 | 37 | 60.9543781(20) | 243(9) ms | β− | 61Mn | (5/2−) | ||||||||||||
62Cr | 24 | 38 | 61.9561429(37) | 206(12) ms | β− | 62Mn | 0+ | ||||||||||||
63Cr | 24 | 39 | 62.961161(78) | 129(2) ms | β− | 63Mn | 1/2−# | ||||||||||||
64Cr | 24 | 40 | 63.96389(32) | 43(1) ms | β− | 64Mn | 0+ | ||||||||||||
65Cr | 24 | 41 | 64.96961(22)# | 27.5(21) ms | β− | 65Mn | 1/2−# | ||||||||||||
66Cr | 24 | 42 | 65.97301(32)# | 23.8(18) ms | β− | 66Mn | 0+ | ||||||||||||
67Cr | 24 | 43 | 66.97931(43)# | 11# ms [>300 ns] | 1/2−# | ||||||||||||||
68Cr | 24 | 44 | 67.98316(54)# | 10# ms [>620 ns] | 0+ | ||||||||||||||
69Cr | 24 | 45 | 68.98966(54)# | 6# ms [>620 ns] | 7/2+# | ||||||||||||||
70Cr | 24 | 46 | 69.99395(64)# | 6# ms [>620 ns] | 0+ | ||||||||||||||
This table header & footer: |
EC: | Electron capture |
IT: | Isomeric transition |
p: | Proton emission |
Chromium-51 is a synthetic radioactive isotope of chromium having a half-life of 27.70 days and decaying by electron capture and emitting a 320-keV gamma ray; it is used to label red blood cells for measurement of mass or volume, survival time, and sequestration studies, for the diagnosis of gastrointestinal bleeding, and to label platelets to study their survival. It has a role as a radioactive label. Chromium-51 has been used as a radioactive label for decades. It is used as a diagnostic radiopharmaceutical agent in nephrology to determine glomerular filtration rate, and in hematology to determine red blood cell volume or mass, study the red blood cell survival time and evaluate blood loss. [6]
Daughter products other than chromium