Naturally occurring
chromium (
24Cr) is composed of four stable
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
s;
50Cr,
52Cr,
53Cr, and
54Cr with
52Cr being the most abundant (83.789%
natural abundance
In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomi ...
).
50Cr is suspected of decaying by
β+β+ to
50Ti with a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of (more than) 1.8×10
17 years. Twenty-two
radioisotope
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s, all of which are entirely synthetic, have been characterized with the most stable being
51Cr with a half-life of 27.7 days. All of the remaining
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...
isotopes have half-lives that are less than 24 hours and the majority of these have half-lives that are less than 1 minute, the least stable being
66Cr with a half-life of 10 milliseconds. This element also has 2
meta state
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...
s,
45mCr, the more stable one, and
59mCr, the least stable isotope or isomer.
53Cr is the
radiogenic
A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay. It may itself be radioactive (a radionuclide) or stable (a stable nuclide).
Radiogenic nuclides (more commonly referred to as radiogenic isotopes) form some ...
decay product of
53 Mn. Chromium
isotopic contents are typically combined with
manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
isotopic contents and have found application in
isotope geology
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope ratio mass spectrometry, and can reveal ...
.
Mn-Cr isotope ratios reinforce the evidence from
26 Al and
107 Pd for the early history of the
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
. Variations in
53Cr/
52Cr and Mn/Cr ratios from several meteorites indicate an initial
53Mn/
55Mn ratio that suggests Mn-Cr isotope systematics must result from in-situ decay of
53Mn in differentiated planetary bodies. Hence
53Cr provides additional evidence for
nucleosynthetic
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...
processes immediately before coalescence of the Solar System. The same isotope is preferentially involved in certain
leaching
Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to:
* Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...
reactions, thereby allowing its abundance in seawater sediments to be used as a proxy for atmospheric oxygen concentrations.
[
]
The isotopes of chromium range from
42Cr to
67Cr. The primary
decay mode before the most abundant stable isotope,
52Cr, is
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...
and the primary mode after is
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
.
List of isotopes
, -
, rowspan=2,
42Cr
, rowspan=2 style="text-align:right" , 24
, rowspan=2 style="text-align:right" , 18
, rowspan=2, 42.00643(32)#
, rowspan=2, 14(3) ms
3(+4-2) ms,
β+ (>99.9%)
,
42V
, rowspan=2, 0+
, rowspan=2,
, rowspan=2,
, -
,
2p (<.1%)
,
40Ti
, -
, rowspan=4,
43Cr
, rowspan=4 style="text-align:right" , 24
, rowspan=4 style="text-align:right" , 19
, rowspan=4, 42.99771(24)#
, rowspan=4, 21.6(7) ms
, β
+ (71%)
,
43V
, rowspan=4, (3/2+)
, rowspan=4,
, rowspan=4,
, -
, β
+, p (23%)
,
42Ti
, -
, β
+, 2p (6%)
,
41Sc
, -
, β
+,
α (<.1%)
,
39Sc
, -
, rowspan=2,
44Cr
, rowspan=2 style="text-align:right" , 24
, rowspan=2 style="text-align:right" , 20
, rowspan=2, 43.98555(5)#
, rowspan=2, 54(4) ms
3(+4-3) ms, β
+ (93%)
,
44V
, rowspan=2, 0+
, rowspan=2,
, rowspan=2,
, -
, β
+, p (7%)
,
43Ti
, -
, rowspan=2,
45Cr
, rowspan=2 style="text-align:right" , 24
, rowspan=2 style="text-align:right" , 21
, rowspan=2, 44.97964(54)
, rowspan=2, 50(6) ms
, β
+ (73%)
,
45V
, rowspan=2, 7/2−#
, rowspan=2,
, rowspan=2,
, -
, β
+, p (27%)
,
44Ti
, -
, rowspan=2 style="text-indent:1em" ,
45mCr
, rowspan=2 colspan="3" style="text-indent:2em" , 50(100)# keV
, rowspan=2, 1# ms
,
IT
,
45Cr
, rowspan=2, 3/2+#
, rowspan=2,
, rowspan=2,
, -
, β
+
,
45V
, -
,
46Cr
, style="text-align:right" , 24
, style="text-align:right" , 22
, 45.968359(21)
, 0.26(6) s
, β
+
,
46V
, 0+
,
,
, -
,
47Cr
, style="text-align:right" , 24
, style="text-align:right" , 23
, 46.962900(15)
, 500(15) ms
, β
+
,
47V
, 3/2−
,
,
, -
,
48Cr
, style="text-align:right" , 24
, style="text-align:right" , 24
, 47.954032(8)
, 21.56(3) h
, β
+
,
48V
, 0+
,
,
, -
,
49Cr
, style="text-align:right" , 24
, style="text-align:right" , 25
, 48.9513357(26)
, 42.3(1) min
, β
+
,
49V
, 5/2−
,
,
, -
,
50Cr
, style="text-align:right" , 24
, style="text-align:right" , 26
, 49.9460442(11)
, colspan=3 align=center,
Observationally Stable
Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes.
Th ...
[Suspected of decaying by double electron capture to 50Ti with a half-life of no less than 1.3 a]
, 0+
, 0.04345(13)
, 0.04294–0.04345
, -
,
51Cr
, style="text-align:right" , 24
, style="text-align:right" , 27
, 50.9447674(11)
, 27.7025(24) d
,
EC
,
51V
, 7/2−
,
,
, -
,
52Cr
, style="text-align:right" , 24
, style="text-align:right" , 28
, 51.9405075(8)
, colspan=3 align=center, Stable
, 0+
, 0.83789(18)
, 0.83762–0.83790
, -
,
53Cr
, style="text-align:right" , 24
, style="text-align:right" , 29
, 52.9406494(8)
, colspan=3 align=center, Stable
, 3/2−
, 0.09501(17)
, 0.09501–0.09553
, -
,
54Cr
, style="text-align:right" , 24
, style="text-align:right" , 30
, 53.9388804(8)
, colspan=3 align=center, Stable
, 0+
, 0.02365(7)
, 0.02365–0.02391
, -
,
55Cr
, style="text-align:right" , 24
, style="text-align:right" , 31
, 54.9408397(8)
, 3.497(3) min
, β
−
,
55Mn
, 3/2−
,
,
, -
,
56Cr
, style="text-align:right" , 24
, style="text-align:right" , 32
, 55.9406531(20)
, 5.94(10) min
, β
−
,
56Mn
, 0+
,
,
, -
,
57Cr
, style="text-align:right" , 24
, style="text-align:right" , 33
, 56.943613(2)
, 21.1(10) s
, β
−
,
57Mn
, (3/2−)
,
,
, -
,
58Cr
, style="text-align:right" , 24
, style="text-align:right" , 34
, 57.94435(22)
, 7.0(3) s
, β
−
,
58Mn
, 0+
,
,
, -
,
59Cr
, style="text-align:right" , 24
, style="text-align:right" , 35
, 58.94859(26)
, 460(50) ms
, β
−
,
59Mn
, 5/2−#
,
,
, -
, style="text-indent:1em" ,
59mCr
, colspan="3" style="text-indent:2em" , 503.0(17) keV
, 96(20) µs
,
,
, (9/2+)
,
,
, -
,
60Cr
, style="text-align:right" , 24
, style="text-align:right" , 36
, 59.95008(23)
, 560(60) ms
, β
−
,
60Mn
, 0+
,
,
, -
, rowspan=2,
61Cr
, rowspan=2 style="text-align:right" , 24
, rowspan=2 style="text-align:right" , 37
, rowspan=2, 60.95472(27)
, rowspan=2, 261(15) ms
, β
− (>99.9%)
,
61Mn
, rowspan=2, 5/2−#
, rowspan=2,
, rowspan=2,
, -
, β
−,
n (<.1%)
,
60Mn
, -
, rowspan=2,
62Cr
, rowspan=2 style="text-align:right" , 24
, rowspan=2 style="text-align:right" , 38
, rowspan=2, 61.95661(36)
, rowspan=2, 199(9) ms
, β
− (>99.9%)
,
62Mn
, rowspan=2, 0+
, rowspan=2,
, rowspan=2,
, -
, β
−, n
,
61Mn
, -
, rowspan=2,
63Cr
, rowspan=2 style="text-align:right" , 24
, rowspan=2 style="text-align:right" , 39
, rowspan=2, 62.96186(32)#
, rowspan=2, 129(2) ms
, β
−
,
63Mn
, rowspan=2, (1/2−)#
, rowspan=2,
, rowspan=2,
, -
, β
−, n
,
62Mn
, -
,
64Cr
, style="text-align:right" , 24
, style="text-align:right" , 40
, 63.96441(43)#
, 43(1) ms
, β
−
,
64Mn
, 0+
,
,
, -
,
65Cr
, style="text-align:right" , 24
, style="text-align:right" , 41
, 64.97016(54)#
, 27(3) ms
, β
−
,
65Mn
, (1/2−)#
,
,
, -
,
66Cr
, style="text-align:right" , 24
, style="text-align:right" , 42
, 65.97338(64)#
, 10(6) ms
, β
−
,
66Mn
, 0+
,
,
, -
,
67Cr
, style="text-align:right" , 24
, style="text-align:right" , 43
, 66.97955(75)#
, 10# ms
300 ns, β
−
,
67Mn
, 1/2−#
,
,
Chromium-51
Chromium-51 is a manmade isotope of chromium used in medicine as a radioisotopic tracer.
References
* Isotope masses from:
**
* Isotopic compositions and standard atomic masses from:
**
**
* Half-life, spin, and isomer data selected from the following sources.
**
**
**
External links
Chromium isotopes data from ''The Berkeley Laboratory Isotopes Project's''
{{Navbox element isotopes
Chromium
Chromium