Calcium Calcium is a chemical element; it has 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 ...

(Ca) has 26 known isotopes, ranging from Ca to Ca. There are five

stable isotope Stable nuclides are Isotope, isotopes of a chemical element whose Nucleon, nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The Atomic nucleus, nuclei of such isotopes are no ...

s (Ca, Ca, Ca, Ca and Ca), plus one isotope ( Ca) with such a long

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

that it is for all practical purposes stable. The most abundant isotope, Ca, as well as the rare Ca, are theoretically unstable on energetic grounds, but their decay has not been observed. Calcium also has a

cosmogenic isotope Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an '' in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom ...

, Ca, with

99,400 years. Unlike

s that are produced in the

air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

, Ca is produced by

neutron activation Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emi ...

of Ca. Most of its production is in the upper metre of the soil column, where the cosmogenic neutron flux is still strong enough. Ca has received much attention in stellar studies because it decays to K, a critical indicator of solar system anomalies. The most stable artificial isotopes are Ca with half-life 163 days and Ca with half-life 4.5 days. All other calcium isotopes have half-lives of minutes or less. Stable Ca comprises about 97% of natural calcium and is mainly created by nucleosynthesis in large stars. Similarly to Ar, however, some atoms of Ca are radiogenic, created through the radioactive decay of K. While

K–Ar dating Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on the measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potas ...

has been used extensively in the

geological Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

sciences, the prevalence of Ca in nature initially impeded the proliferation of K-Ca dating in early studies, with only a handful of studies in the 20th century. Modern techniques using increasingly precise Thermal-Ionization ( TIMS) and Collision-Cell Multi-Collector Inductively-coupled plasma

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...

( CC-MC-ICP-MS) techniques, however, have been used for successful K–Ca age dating, as well as determining K losses from the lower continental crust and for source-tracing calcium contributions from various geologic reservoirs similar to Rb-Sr. Stable isotope variations of calcium (most typically Ca/Ca or ⁴⁴Ca/⁴²Ca, denoted as 'δCa' and 'δCa' in delta notation) are also widely used across the natural sciences for a number of applications, ranging from early determination of

osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to more porous bone, and consequent increase in Bone fracture, fracture risk. It is the most common reason f ...

to quantifying

volcanic eruption A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior h ...

timescales. Other applications include: quantifying

carbon sequestration Carbon sequestration is the process of storing carbon in a carbon pool. It plays a crucial role in Climate change mitigation, limiting climate change by reducing the amount of Carbon dioxide in Earth's atmosphere, carbon dioxide in the atmosphe ...

efficiency in CO₂ injection sites and understanding

ocean acidification Ocean acidification is the ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ...

, exploring both ubiquitous and rare magmatic processes, such as formation of

granites Granite ( ) is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

and carbonatites, tracing modern and ancient trophic webs including in dinosaurs, assessing

weaning Weaning is the process of gradually introducing an infant human or other mammal to what will be its adult diet while withdrawing the supply of its mother's milk. In the United Kingdom, UK, weaning primarily refers to the introduction of solid ...

practices in ancient humans, and a plethora of other emerging applications.

List of isotopes

, -id=Calcium-35 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 15 , rowspan=3, 35.00557(22)# , rowspan=3, 25.7(2) ms , β, p (95.8%) , Ar , rowspan=3, 1/2+# , rowspan=3, , rowspan=3, , - , β, 2p (4.2%) , Cl , - , β (rare) , K , -id=Calcium-36 , rowspan=2, Ca , rowspan=2 style="text-align:right" , 20 , rowspan=2 style="text-align:right" , 16 , rowspan=2, 35.993074(43) , rowspan=2, 100.9(13) ms , β, p (51.2%) , Ar , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β (48.8%) , K , -id=Calcium-37 , rowspan=2, Ca , rowspan=2 style="text-align:right" , 20 , rowspan=2 style="text-align:right" , 17 , rowspan=2, 36.98589785(68) , rowspan=2, 181.0(9) ms , β, p (76.8%) , Ar , rowspan=2, 3/2+ , rowspan=2, , rowspan=2, , - , β (23.2%) , K , -id=Calcium-38 , Ca , style="text-align:right" , 20 , style="text-align:right" , 18 , 37.97631922(21) , 443.70(25) ms , β , K , 0+ , , , -id=Calcium-39 , Ca , style="text-align:right" , 20 , style="text-align:right" , 19 , 38.97071081(64) , 860.3(8) ms , β , K , 3/2+ , , , -id=Calcium-40 , CaHeaviest observationally stable nuclide with equal numbers of protons and neutrons , style="text-align:right" , 20 , style="text-align:right" , 20 , 39.962590850(22) , colspan=3 align=center,

Observationally stable Stable nuclides are isotopes of a chemical element whose nucleons are in a configuration that does not permit them the surplus energy required to produce a radioactive emission. The nuclei of such isotopes are not radioactive and unlike radionuc ...

Believed to undergo

double electron capture Double electron capture is a decay mode of an atomic nucleus. For a nuclide (''A'', ''Z'') with a number of nucleons ''A'' and atomic number ''Z'', double electron capture is only possible if the mass of the nuclide (''A'', ''Z''−2) is lower. I ...

to Ar with a half-life no less than 9.9×10 y , 0+ , 0.9694(16) , 0.96933–0.96947 , -id=Calcium-41 , Ca , style="text-align:right" , 20 , style="text-align:right" , 21 , 40.96227791(15) , 9.94(15)×10 y , EC , K , 7/2− , Trace

Cosmogenic nuclide Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an '' in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom ...

, , -id=Calcium-42 , Ca , style="text-align:right" , 20 , style="text-align:right" , 22 , 41.95861778(16) , colspan=3 align=center, Stable , 0+ , 0.00647(23) , 0.00646–0.00648 , -id=Calcium-43 , Ca , style="text-align:right" , 20 , style="text-align:right" , 23 , 42.95876638(24) , colspan=3 align=center, Stable , 7/2− , 0.00135(10) , 0.00135–0.00135 , -id=Calcium-44 , Ca , style="text-align:right" , 20 , style="text-align:right" , 24 , 43.95548149(35) , colspan=3 align=center, Stable , 0+ , 0.0209(11) , 0.02082–0.02092 , -id=Calcium-45 , Ca , style="text-align:right" , 20 , style="text-align:right" , 25 , 44.95618627(39) , 162.61(9) d , β , Sc , 7/2− , , , -id=Calcium-46 , Ca , style="text-align:right" , 20 , style="text-align:right" , 26 , 45.9536877(24) , colspan=3 align=center, Observationally stableBelieved to undergo ββ decay to Ti , 0+ , 4×10 , 4×10–4×10 , -id=Calcium-47 , Ca , style="text-align:right" , 20 , style="text-align:right" , 27 , 46.9545411(24) , 4.536(3) d , β , Sc , 7/2− , , , - , Ca Primordial

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

Believed to be capable of undergoing triple beta decay with very long partial half-life , style="text-align:right" , 20 , style="text-align:right" , 28 , 47.952522654(18) , 5.6(10)×10 y, , ββLightest nuclide known to undergo

double beta decay In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move cl ...

, Ti , 0+ , 0.00187(21) , 0.00186–0.00188 , -id=Calcium-49 , Ca , style="text-align:right" , 20 , style="text-align:right" , 29 , 48.95566263(19) , 8.718(6) min , β , Sc , 3/2− , , , -id=Calcium-50 , Ca , style="text-align:right" , 20 , style="text-align:right" , 30 , 49.9574992(17) , 13.45(5) s , β , Sc , 0+ , , , -id=Calcium-51 , rowspan=2, Ca , rowspan=2 style="text-align:right" , 20 , rowspan=2 style="text-align:right" , 31 , rowspan=2, 50.96099566(56) , rowspan=2, 10.0(8) s , β , Sc , rowspan=2, 3/2− , rowspan=2, , rowspan=2, , - , β, n? , Sc , -id=Calcium-52 , rowspan=2, Ca , rowspan=2 style="text-align:right" , 20 , rowspan=2 style="text-align:right" , 32 , rowspan=2, 51.96321365(72) , rowspan=2, 4.6(3) s , β (>98%) , Sc , rowspan=2, 0+ , rowspan=2, , rowspan=2, , - , β, n (<2%) , Sc , -id=Calcium-53 , rowspan=2, Ca , rowspan=2 style="text-align:right" , 20 , rowspan=2 style="text-align:right" , 33 , rowspan=2, 52.968451(47) , rowspan=2, 461(90) ms , β (60%) , Sc , rowspan=2, 1/2−# , rowspan=2, , rowspan=2, , - , β, n (40%) , Sc , -id=Calcium-54 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 34 , rowspan=3, 53.972989(52) , rowspan=3, 90(6) ms , β , Sc , rowspan=3, 0+ , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc , -id=Calcium-55 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 35 , rowspan=3, 54.97998(17) , rowspan=3, 22(2) ms , β , Sc , rowspan=3, 5/2−# , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc , -id=Calcium-56 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 36 , rowspan=3, 55.98550(27) , rowspan=3, 11(2) ms , β , Sc , rowspan=3, 0+ , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc , -id=Calcium-57 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 37 , rowspan=3, 56.99296(43)# , rowspan=3, 8# ms 620 ns, β? , Sc , rowspan=3, 5/2−# , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc , -id=Calcium-58 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 38 , rowspan=3, 57.99836(54)# , rowspan=3, 4# ms 620 ns, β? , Sc , rowspan=3, 0+ , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc , -id=Calcium-59 , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 39 , rowspan=3, 59.00624(64)# , rowspan=3, 5# ms 400 ns, β? , Sc , rowspan=3, 5/2−# , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc , - , rowspan=3, Ca , rowspan=3 style="text-align:right" , 20 , rowspan=3 style="text-align:right" , 40 , rowspan=3, 60.01181(75)# , rowspan=3, 2# ms 400 ns, β? , Sc , rowspan=3, 0+ , rowspan=3, , rowspan=3, , - , β, n? , Sc , - , β, 2n? , Sc

Calcium-48

Calcium-48 is a doubly magic nucleus with 28 neutrons; unusually neutron-rich for a light primordial nucleus. It decays via

with an extremely long half-life of about 6.4×10 years, though single beta decay is also theoretically possible. This decay can analyzed with the ''sd''

nuclear shell model In nuclear physics, atomic physics, and nuclear chemistry, the nuclear shell model utilizes the Pauli exclusion principle to model the structure of atomic nuclei in terms of energy levels. The first shell model was proposed by Dmitri Ivanenk ...

, and it is more energetic (4.27

MeV In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum. When us ...

) than any other double beta decay. It can also be used as a precursor for neutron-rich and superheavy nuclei.

Calcium-60

Calcium-60 is the heaviest known isotope . First observed in 2018 at

Riken is a national scientific research institute in Japan. Founded in 1917, it now has about 3,000 scientists on seven campuses across Japan, including the main site at Wakō, Saitama, Wakō, Saitama Prefecture, on the outskirts of Tokyo. Riken is a ...

alongside Ca and seven isotopes of other elements, its existence suggests that there are additional even-''N'' isotopes of calcium up to at least Ca, while Ca is probably the last bound isotope with odd ''N''. Earlier predictions had estimated the neutron drip line to occur at Ca, with Ca unbound. In the neutron-rich region, ''N'' = 40 becomes a magic number, so Ca was considered early on to be a possibly doubly magic nucleus, as is observed for the Ni

isotone Two nuclides are isotones if they have the same neutron number ''N'', but different proton number ''Z''. For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones. Similarly, 36S, 37Cl, 38Ar, 39K, and 40Ca nucle ...

. However, subsequent spectroscopic measurements of the nearby nuclides Ca, Ca, and Ti instead predict that it should lie on the island of inversion known to exist around Cr.

References

External links

National Isotope Development Center Official website
{{Authority control Calcium

List of isotopes

Calcium-48

Calcium-60

See also

References

Further reading

External links