The alkaline earth metal

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 of ...

; 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 × 10¹⁰ years (i.e. more than three times longer than the current age 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). 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 (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 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

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. 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, bē̂ta or ell, βήτα, víta) 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 StableBelieved 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+ , , , - , ⁸⁷SrUsed in rubidium–strontium dating , 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 ...