The
alkaline earth metal
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are al ...
strontium
Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
(
38Sr) has four stable, naturally occurring
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 numbers) ...
s:
84Sr (0.56%),
86Sr (9.86%),
87Sr (7.0%) and
88Sr (82.58%). Its
standard atomic weight
The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, is ...
is 87.62(1).
Only
87Sr is
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 ...
; it is produced by decay from the
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 consid ...
alkali metal
87 Rb, which has 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 ato ...
of 4.88 × 10
10 years (i.e. more than three times longer than the current
age of the universe
In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Astronomers have derived two different measurements of the age of the universe:
a measurement based on direct observations of an early state of the universe, ...
). Thus, there are two sources of
87Sr in any material: primordial, formed during nucleosynthesis along with
84Sr,
86Sr and
88Sr; and that formed by radioactive decay of
87Rb. The ratio
87Sr/
86Sr is the parameter typically reported in
geologic
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
investigations; ratios in minerals and
rock
Rock most often refers to:
* Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids
* Rock music, a genre of popular music
Rock or Rocks may also refer to:
Places United Kingdom
* Rock, Caerphilly, a location in Wales ...
s have values ranging from about 0.7 to greater than 4.0 (see
rubidium–strontium dating
The rubidium-strontium dating method is a radiometric dating technique, used by scientists to determine the age of rocks and minerals from their content of specific isotopes of rubidium (87Rb) and strontium (87Sr, 86Sr). One of the two naturally ...
). Because strontium has an
electron configuration
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom ...
similar to that of
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
, it readily substitutes for calcium in
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
s.
In addition to the four stable isotopes, thirty-two unstable isotopes of strontium are known to exist, ranging from
73Sr to
108Sr. Radioactive isotopes of strontium primarily decay into the neighbouring elements
yttrium
Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in com ...
(
89Sr and heavier isotopes, via
beta minus 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 exam ...
) and
rubidium
Rubidium is the chemical element with the symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have a density higher ...
(
85Sr,
83Sr and lighter isotopes, via
positron emission
Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron ...
or
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 ...
). The longest-lived of these isotopes, and the most relevantly studied, are
90Sr with a half-life of 28.9 years,
85Sr with a half-life of 64.853 days, and
89Sr (
89Sr) 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 ato ...
of 50.57 days. All other strontium isotopes have half-lives shorter than 50 days, most under 100 minutes.
Strontium-89
Strontium-89 () is a radioactive isotope of strontium produced by nuclear fission, with a half-life of 50.57 days. It undergoes β− decay into yttrium-89. Strontium-89 has an application in medicine.
History
It was used for the first time b ...
is an artificial radioisotope used in treatment of bone cancer; this application utilizes its chemical similarity to calcium, which allows it to substitute calcium in bone structures. In circumstances where cancer patients have widespread and painful bony
metastases
Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...
, the administration of
89Sr results in the delivery of
beta particles
A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β∠...
directly to the area of bony problem, where calcium turnover is greatest.
Strontium-90 is a by-product of
nuclear fission
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...
, present in
nuclear fallout
Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
. The
1986 Chernobyl nuclear accident contaminated a vast area with
90Sr. It causes health problems, as it substitutes for calcium in
bone
A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...
, preventing expulsion from the body. Because it is a long-lived high-energy
beta
Beta (, ; uppercase , lowercase , or cursive ; grc, βῆτα, bÄ“Ì‚ta or ell, βήτα, vÃta) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Modern Greek, it represents the voiced labiod ...
emitter, it is used in SNAP (
Systems for Nuclear Auxiliary Power
The Systems Nuclear Auxiliary POWER (SNAP) program was a program of experimental radioisotope thermoelectric generators (RTGs) and space nuclear reactors flown during the 1960s by NASA.
Odd-numbered SNAPs: radioisotope thermoelectric generators ...
) devices. These devices hold promise for use in
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is required.
In 2020, researchers have found that
mirror nuclides 73Sr and
73Br were found to not behave identically to each other as expected.
List of isotopes
, -
, rowspan=2,
73Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 35
, rowspan=2, 72.96597(64)#
, rowspan=2, >25 ms
,
β+ (>99.9%)
,
73Rb
, rowspan=2, 1/2−#
, rowspan=2,
, rowspan=2,
, -
, β
+,
p (<.1%)
,
72Kr
, -
,
74Sr
, style="text-align:right" , 38
, style="text-align:right" , 36
, 73.95631(54)#
, 50# ms
1.5 µs, β
+
,
74Rb
, 0+
,
,
, -
, rowspan=2,
75Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 37
, rowspan=2, 74.94995(24)
, rowspan=2, 88(3) ms
, β
+ (93.5%)
,
75Rb
, rowspan=2, (3/2−)
, rowspan=2,
, rowspan=2,
, -
, β
+, p (6.5%)
,
74Kr
, -
,
76Sr
, style="text-align:right" , 38
, style="text-align:right" , 38
, 75.94177(4)
, 7.89(7) s
, β
+
,
76Rb
, 0+
,
,
, -
, rowspan=2,
77Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 39
, rowspan=2, 76.937945(10)
, rowspan=2, 9.0(2) s
, β
+ (99.75%)
,
77Rb
, rowspan=2, 5/2+
, rowspan=2,
, rowspan=2,
, -
, β
+, p (.25%)
,
76Kr
, -
,
78Sr
, style="text-align:right" , 38
, style="text-align:right" , 40
, 77.932180(8)
, 159(8) s
, β
+
,
78Rb
, 0+
,
,
, -
,
79Sr
, style="text-align:right" , 38
, style="text-align:right" , 41
, 78.929708(9)
, 2.25(10) min
, β
+
,
79Rb
, 3/2(−)
,
,
, -
,
80Sr
, style="text-align:right" , 38
, style="text-align:right" , 42
, 79.924521(7)
, 106.3(15) min
, β
+
,
80Rb
, 0+
,
,
, -
,
81Sr
, style="text-align:right" , 38
, style="text-align:right" , 43
, 80.923212(7)
, 22.3(4) min
, β
+
,
81Rb
, 1/2−
,
,
, -
,
82Sr
, style="text-align:right" , 38
, style="text-align:right" , 44
, 81.918402(6)
, 25.36(3) d
,
EC
,
82Rb
, 0+
,
,
, -
,
83Sr
, style="text-align:right" , 38
, style="text-align:right" , 45
, 82.917557(11)
, 32.41(3) h
, β
+
,
83Rb
, 7/2+
,
,
, -
, style="text-indent:1em" ,
83mSr
, colspan="3" style="text-indent:2em" , 259.15(9) keV
, 4.95(12) s
, IT
,
83Sr
, 1/2−
,
,
, -
,
84Sr
, style="text-align:right" , 38
, style="text-align:right" , 46
, 83.913425(3)
, 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 ...
[Believed to decay by β+β+ to 84Kr]
, 0+
, 0.0056
, 0.0055–0.0058
, -
,
85Sr
, style="text-align:right" , 38
, style="text-align:right" , 47
, 84.912933(3)
, 64.853(8) d
, EC
,
85Rb
, 9/2+
,
,
, -
, rowspan=2 style="text-indent:1em" ,
85mSr
, rowspan=2 colspan="3" style="text-indent:2em" , 238.66(6) keV
, rowspan=2, 67.63(4) min
, IT (86.6%)
,
85Sr
, rowspan=2, 1/2−
, rowspan=2,
, rowspan=2,
, -
, β
+ (13.4%)
,
85Rb
, -
,
86Sr
, style="text-align:right" , 38
, style="text-align:right" , 48
, 85.9092607309(91)
, colspan=3 align=center, Stable
, 0+
, 0.0986
, 0.0975–0.0999
, -
, style="text-indent:1em" ,
86mSr
, colspan="3" style="text-indent:2em" , 2955.68(21) keV
, 455(7) ns
,
,
, 8+
,
,
, -
,
87Sr
[Used in ]rubidium–strontium dating
The rubidium-strontium dating method is a radiometric dating technique, used by scientists to determine the age of rocks and minerals from their content of specific isotopes of rubidium (87Rb) and strontium (87Sr, 86Sr). One of the two naturally ...
, style="text-align:right" , 38
, style="text-align:right" , 49
, 86.9088774970(91)
, colspan=3 align=center, Stable
, 9/2+
, 0.0700
, 0.0694–0.0714
, -
, rowspan=2 style="text-indent:1em" ,
87mSr
, rowspan=2 colspan="3" style="text-indent:2em" , 388.533(3) keV
, rowspan=2, 2.815(12) h
, IT (99.7%)
,
87Sr
, rowspan=2, 1/2−
, rowspan=2,
, rowspan=2,
, -
, EC (.3%)
, ''
87Rb''
, -
,
88Sr
Fission product
Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...
, style="text-align:right" , 38
, style="text-align:right" , 50
, 87.9056122571(97)
, colspan=3 align=center, Stable
, 0+
, 0.8258
, 0.8229–0.8275
, -
,
89Sr
, style="text-align:right" , 38
, style="text-align:right" , 51
, 88.9074507(12)
, 50.57(3) d
, β
−
,
89Y
, 5/2+
,
,
, -
,
90Sr
, style="text-align:right" , 38
, style="text-align:right" , 52
, 89.907738(3)
, 28.90(3) y
, β
−
,
90Y
, 0+
,
,
, -
,
91Sr
, style="text-align:right" , 38
, style="text-align:right" , 53
, 90.910203(5)
, 9.63(5) h
, β
−
,
91Y
, 5/2+
,
,
, -
,
92Sr
, style="text-align:right" , 38
, style="text-align:right" , 54
, 91.911038(4)
, 2.66(4) h
, β
−
,
92Y
, 0+
,
,
, -
,
93Sr
, style="text-align:right" , 38
, style="text-align:right" , 55
, 92.914026(8)
, 7.423(24) min
, β
−
,
93Y
, 5/2+
,
,
, -
,
94Sr
, style="text-align:right" , 38
, style="text-align:right" , 56
, 93.915361(8)
, 75.3(2) s
, β
−
,
94Y
, 0+
,
,
, -
,
95Sr
, style="text-align:right" , 38
, style="text-align:right" , 57
, 94.919359(8)
, 23.90(14) s
, β
−
,
95Y
, 1/2+
,
,
, -
,
96Sr
, style="text-align:right" , 38
, style="text-align:right" , 58
, 95.921697(29)
, 1.07(1) s
, β
−
,
96Y
, 0+
,
,
, -
, rowspan=2,
97Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 59
, rowspan=2, 96.926153(21)
, rowspan=2, 429(5) ms
, β
− (99.95%)
,
97Y
, rowspan=2, 1/2+
, rowspan=2,
, rowspan=2,
, -
, β
−,
n (.05%)
,
96Y
, -
, style="text-indent:1em" ,
97m1Sr
, colspan="3" style="text-indent:2em" , 308.13(11) keV
, 170(10) ns
,
,
, (7/2)+
,
,
, -
, style="text-indent:1em" ,
97m2Sr
, colspan="3" style="text-indent:2em" , 830.8(2) keV
, 255(10) ns
,
,
, (11/2−)#
,
,
, -
, rowspan=2,
98Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 60
, rowspan=2, 97.928453(28)
, rowspan=2, 0.653(2) s
, β
− (99.75%)
,
98Y
, rowspan=2, 0+
, rowspan=2,
, rowspan=2,
, -
, β
−, n (.25%)
,
97Y
, -
, rowspan=2,
99Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 61
, rowspan=2, 98.93324(9)
, rowspan=2, 0.269(1) s
, β
− (99.9%)
,
99Y
, rowspan=2, 3/2+
, rowspan=2,
, rowspan=2,
, -
, β
−, n (.1%)
,
98Y
, -
, rowspan=2,
100Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 62
, rowspan=2, 99.93535(14)
, rowspan=2, 202(3) ms
, β
− (99.02%)
,
100Y
, rowspan=2, 0+
, rowspan=2,
, rowspan=2,
, -
, β
−, n (.98%)
,
99Y
, -
, rowspan=2,
101Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 63
, rowspan=2, 100.94052(13)
, rowspan=2, 118(3) ms
, β
− (97.63%)
,
101Y
, rowspan=2, (5/2−)
, rowspan=2,
, rowspan=2,
, -
, β
−, n (2.37%)
,
100Y
, -
, rowspan=2,
102Sr
, rowspan=2 style="text-align:right" , 38
, rowspan=2 style="text-align:right" , 64
, rowspan=2, 101.94302(12)
, rowspan=2, 69(6) ms
, β
− (94.5%)
,
102Y
, rowspan=2, 0+
, rowspan=2,
, rowspan=2,
, -
, β
−, n (5.5%)
,
101Y
, -
,
103Sr
, style="text-align:right" , 38
, style="text-align:right" , 65
, 102.94895(54)#
, 50# ms
300 ns, β
−
,
103Y
,
,
,
, -
,
104Sr
, style="text-align:right" , 38
, style="text-align:right" , 66
, 103.95233(75)#
, 30# ms
300 ns, β
−
,
104Y
, 0+
,
,
, -
,
105Sr
, style="text-align:right" , 38
, style="text-align:right" , 67
, 104.95858(75)#
, 20# ms
300 ns,
,
,
,
,
, -
,
106Sr
, style="text-align:right" , 38
, style="text-align:right" , 68
,
,
,
,
,
,
,
, -
,
107Sr
, style="text-align:right" , 38
, style="text-align:right" , 69
,
,
,
,
,
,
,
, -
,
108Sr
, style="text-align:right" , 38
, style="text-align:right" , 70
,
,
,
,
,
,
,
References
* Isotope masses from:
**
* Isotopic compositions and standard atomic masses from:
**
**
* Half-life, spin, and isomer data selected from the following sources.
**
**
**
{{Authority control
Strontium
Strontium
Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...