It’s Elemental — Isotopes of the Element Calcium

Atomic Weight of Calcium | Commission on Isotopic Abundances and Atomic Weights

Common reference compound: CaCl2/D2O, 0.1 M.

Isotope Atomic mass (Da) Isotopic abundance (amount fraction)
40Ca 39.962 5909(2) 0.969 41(156)
42Ca 41.958 618(1) 0.006 47(23)
43Ca 42.958 766(2) 0.001 35(10)
44Ca 43.955 482(2) 0.020 86(110)
46Ca 45.953 69(2) 0.000 04(3)
48Ca 47.952 5229(6) 0.001 87(21)

In 1983, the Commission with its liberalized policy on uncertainties,
was able to recommend as standard atomic weight Ar(Ca) = 40.078(4) weighted toward the mass-spectrometric
measurements. Moreover, the stated uncertainty includes all chemical,
x-ray, and mass-spectrometric measurements believed to be significant by the Commission, as enumerated in
its 1983 report.

There is evidence for minor isotope fractionation of calcium in Nature, causing variability of
Ar(Ca) in normal sources that is within the uncertainty of the standard atomic weight. Variations in
n(44Ca)/n(40Ca) can be reported as δ44Ca values relative to the calcium carbonate reference material
NIST-SRM 915a. A recent compilation yielded a range of published δ44Ca values in natural
samples from a low of -2.17 ‰ in a cougar bone with Ar(Ca) = 40.0778 to a high of 2.76 ‰ in egg white with Ar(Ca) = 40.0784.
Elemental calcium with as δ44Ca = -6.0 ‰ (Ar(Ca) = 40.0773) also has been
reported. Variations in the isotopic composition of marine calcium have occurred over the last 80 Ma.

In addition, there are many reports of anomalous isotopic composition of some minor samples of Ca,
some of which may have arisen from the decay of 40K to 40Ca. The annotation «g» is therefore maintained for this element.
41Ca is an extinct radioisotope (with a half-life of 0.1 Ma), which can be used to date the early history of the solar system through its
decay to 41K.

SOURCE  Atomic weights of the elements: Review 2000 by John R de Laeter et al. Pure Appl. Chem. 2003 (75) 683-800
© IUPAC 2003

Transcript :

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You’re listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

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Chris Smith

Hello, welcome to this week’s Chemistry in its Element, I’m Chris Smith. This week it’s the turn of the element that gives us cement, plaster of Paris, our own bones, hard teeth and hard water.

Karen Faulds

Milk, cheese, yogurt, spinach, almonds. What element do they all have in common? It’s calcium of course! But whilst most off us immediately think of food when someone mentions calcium (and I personally hold the old milk TV adverts accountable for this), it actually has a far bigger role in our lives than that. Calcium is all around us. The average human contains approximately 1kg of calcium, of which 99% is stored in our bones. It is the 5th most abundant element in the earth’s crust, occurring widely as calcium carbonate which is more commonly known as limestone. It is also the fifth most abundant dissolved ion in seawater.

Calcium was named after the Latin term calx meaning lime, and is a reactive silvery metallic element found in Group 2 of the periodic table. It was first isolated in 1808 in England when Sir Humphry Davy electrolyzed a mixture of lime and mercuric oxide. Today we obtain calcium through the electrolysis of a fused salt such as calcium chloride. Once exposed to air, elemental calcium rapidly forms a grey-white oxide and nitride coating. Unlike magnesium, calcium is quite difficult to ignite, but once lit, it burns with a brilliant high-intensity red flame.

The compounds of calcium are however much more useful than the element itself. Literature dating back to 975 AD shows that plaster of Paris (which is calcium sulphate) was used even then for setting broken bones. Calcium oxide (also known as lime or quicklime) is a major component of mortar and cement. The production of cement using calcium oxide has long been known; it was used by the Romans and also the Egyptians who built the Great Pyramid of Giza and Tutankhamen’s tomb. Calcium fluoride is also well known for being insoluble and transparent over a wide range of wavelengths, making it useful for making cells and windows for infrared and ultraviolet spectrometers.

Our drinking water also contains calcium ions — more so in so called hard water areas. Hard water is the term used for water with a high proportion of calcium and magnesium (2 plus) ions. The calcium usually enters the water as it flows past either calcium carbonate, from limestone and chalk, or calcium sulfate, from other mineral deposits. Whilst some people do not like the taste, hard water is generally not harmful to your health. Although it does make your kettle furry! Interestingly, the taste of beer (something dear to my heart) seems related to the calcium concentration of the water used, and it is claimed that good beer should have a calcium concentration that is higher than that of hard tap water.

Calcium is what is known as an essential element, meaning that it is an element which is absolutely necessary for life processes. Which is what the old milk TV adverts were trying to tell us after all. Calcium is used to produce the minerals contained in bones, shells and teeth through a process called biomineralisation. Calcium phosphate (also known as hydroxyapatite) is the mineral component of bones and teeth and is a particularly good example of how organisms fabricate ‘living’ composite materials. Indeed, the different properties (such as stiffness) of bone are produced by varying the amount of organic component, mostly a fibrous protein called collagen, with which hydroxyapatite is associated. The bone in our body functions not only as a structural support, but also as the central Ca store. Thus, during pregnancy, bones tend to be raided for their Ca in a process called demineralisation. Bone does not last forever; a serious medical problem is osteoporosis which is the decalcification of bone. This loss of bone mass which occurs with increasing age makes bones more susceptible to breaking under stress and it occurs mainly in older people, especially women.

Calcium ions also play a crucial role in higher organisms as an intracellular messenger. Fluxes of Ca2 trigger enzyme action in cells in response to receiving a hormonal or electrical signal from elsewhere in the organism. Calcium is also very important in helping blood to clot. When bleeding from a wound suddenly occurs, platelets gather at the wound and attempt to block the blood flow. Calcium, vitamin K, and a protein called fibrinogen help the platelets to form a clot. If your blood is lacking calcium or one of these other nutrients, it will take longer than normal for your blood to clot.

The ability to detect extremely small amounts of an element can be a very useful adaptation for an animal if that element is important to it. For example, hermit crabs, which inhabit second hand shells and change to newer, bigger shells as they grow, have the ability to recognise shells suitable for occupation not only by feeling for them, but apparently also by measuring the minute amount of calcium carbonate that is dissolved in the water around a shell. They can readily distinguish natural shells containing calcium carbonate from calcium-bearing replicas made from calcium sulphate. The concentration of calcium detected by the hermit crab is in the order of 4ppm or less, which is amazingly low.

So from strong teeth and bones, through to good tasting beer and ensuring hermit crabs find their perfect home -you can see that calcium really is an essential element.

Chris Smith

Well, I’m very at home with my hard water, and the local beer tastes quite good too, although I do get through quite a few kettles — indeed Russell Hobbs probably owe their buoyant share price just down to me. Well, maybe. That was Strathclyde University’s Karen Faulds with the story of Calcium. Next week, if you were an element which one would you be?

Pat Bailey

If I had to choose a person to represent gold, then I guess it might be an ambitious young stockbroker, a bit flashy, and not great at forming relationships. For helium — an airy-fairy blonde with a bit of a squeaky voice, but with aspirations to join the nobility. And for boron? Well at first glance a boring, middle-aged accountant, maybe wearing brown corduroys and a tweed jacket . but with an unexpected side-to him in his spare time — skydiving, and a member of a highly dubious society that indulges in swapping partners.

Chris Smith

And you can get the inside story on Boron’s swinging antics with Pat Bailey in next week’s Chemistry in its Element. I’m Chris Smith, thank you for listening and goodbye.

(Promo)

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Isotopes of the Element Calcium

[Click for Main Data]

Most of the isotope data on this site has been obtained from the National Nuclear Data Center. Please visit their site for more information.

Isotopes With A Known Natural Abundance

Mass Number Natural Abundance Half-life
40 96.94% {amp}gt; 3.0×10 21 years
42 0.647% STABLE
43 0.135% STABLE
44 2.09% STABLE
46 0.004% {amp}gt; 0.28×10 16 years
48 0.187% {amp}gt; 5.8×1022 years

Known Isotopes

Naturally occurring isotopes

This table shows information about naturally occuring isotopes, their atomic masses, their natural abundances, their nuclear spins, and their magnetic moments. Further data for radioisotopes (radioactive isotopes) of calcium are listed (including any which occur naturally) below.
Isotope Mass / Da Natural abundance (atom %) Nuclear spin (I) Magnetic moment (μ/μN)
40Ca 39.9625906 (13) 96.941 (156) 0 0
42Ca 41.9586176 (13) 0.647 (23) 0 0
43Ca 42.9587662 (13) 0.135 (10) 7/2 -1.31727
44Ca 43.9554806 (14) 2.086 (110) 0 0
46Ca 45.953689 (4) 0.004 (3) 0 0
48Ca 47.952533 (4) 0.187 (21) 0 0
Isotope abundances of calcium
Isotope abundances of calcium. In the above, the most intense ion is set to 100% since this corresponds best to the output from a mass spectrometer. This is not to be confused with the relative percentage isotope abundances which totals 100% for all the naturally occurring isotopes.

Radiosotope data

Further data for naturally occuring isotopes of calcium are listed above. This table gives information about some radiosotopes of calcium, their masses, their half-lives, their modes of decay, their nuclear spins, and their nuclear magnetic moments.
Isotope Mass / Da Half-life Mode of decay Nuclear spin Nuclear magnetic moment
41Ca 40.9622783 102000 y EC to 41K 7/2 -1.595
45Ca 44.956186 162.7 d β to 45Sc 7/2 -1.327
47Ca 46.954546 4.536 d β to 47Sc 7/2 -1.38
49Ca 48.955673 8.72 m β to 49Sc 3/2
50Ca 49.95752 14 s β to 50Sc 0
51Ca 50.9615 10 s β to 51Sc; β n to 50Sc 3/2
52Ca 51.9651 4.6 s β to 52Sc

References

  1. Naturally occurring isotope abundances: Commission on Atomic Weights and Isotopic Abundances report for the International Union of Pure and Applied Chemistry in Isotopic Compositions of the Elements 1989, Pure and Applied Chemistry, 1998, 70, 217. [Copyright 1998 IUPAC]
  2. For further information about radioisotopes see Jonghwa Chang’s (Korea Atomic Energy Research Institute) Table of the Nuclides
  3. Masses, nuclear spins, and magnetic moments: I. Mills, T. Cvitas, K. Homann, N. Kallay, and K. Kuchitsu in Quantities, Units and Symbols in Physical Chemistry, Blackwell Scientific Publications, Oxford, UK, 1988. [Copyright 1988 IUPAC]
  1. R.K. Harris in Encyclopedia of Nuclear Magnetic Resonance, D.M. Granty and R.K. Harris, (eds.), vol. 5, John Wiley {amp}amp; Sons, Chichester, UK, 1996. I am grateful to Professor Robin Harris (University of Durham, UK) who provided much of the NMR data, which are copyright 1996 IUPAC, adapted from his contribution contained within this reference.
  2. J. Mason in Multinuclear NMR, Plenum Press, New York, USA, 1987. Where given, data for certain radioactive nuclei are from this reference.
  3. P. Pyykkö, Mol. Phys., 2008, 106, 1965-1974.
  4. P. Pyykkö, Mol. Phys., 2001, 99, 1617-1629.
  5. P. Pyykkö, Z. Naturforsch., 1992, 47a, 189. I am grateful to Professor Pekka Pyykkö (University of Helsinki, Finland) who provided the nuclear quadrupole moment data in this and the following two references.
  6. D.R. Lide, (ed.), CRC Handbook of Chemistry and Physics 1999-2000 : A Ready-Reference Book of Chemical and Physical Data (CRC Handbook of Chemistry and Physics, CRC Press, Boca Raton, Florida, USA, 79th edition, 1998.
  7. P. Pyykkö, personal communication, 1998, 204, 2008, 2010.

Table 3. List of Elements in Name Order.

At No     Symbol     Name Atomic Wt Notes
89 Ac Actinium [227] 4
13 Al Aluminium 26.981 5384(3)
95 Am Americium [243] 4
51 Sb Antimony 121.760(1) 1
18 Ar Argon 39.948(1) 1, 2, 5
33 As Arsenic 74.921 595(6)
85 At Astatine [210] 4
56 Ba Barium 137.327(7)
97 Bk Berkelium [247] 4
4 Be Beryllium 9.012 1831(5)
83 Bi Bismuth 208.980 40(1)
107 Bh Bohrium [270] 4
5 B Boron 10.81 3, 5
35 Br Bromine 79.904 5
48 Cd Cadmium 112.414(4) 1
55 Cs Caesium 132.905 451 96(6)
20 Ca Calcium 40.078(4) 1
98 Cf Californium [251] 4
6 C Carbon 12.011 5
58 Ce Cerium 140.116(1) 1
17 Cl Chlorine 35.45 3, 5
24 Cr Chromium 51.9961(6)
27 Co Cobalt 58.933 194(3)
112 Cn Copernicium [285] 4
29 Cu Copper 63.546(3) 2
96 Cm Curium [247] 4
110 Ds Darmstadtium [281] 4
105 Db Dubnium [270] 4
66 Dy Dysprosium 162.500(1) 1
99 Es Einsteinium [252] 4
68 Er Erbium 167.259(3) 1
63 Eu Europium 151.964(1) 1
100 Fm Fermium [257] 4
114 Fl Flerovium [289] 4
9 F Fluorine 18.998 403 163(6)
87 Fr Francium [223] 4
64 Gd Gadolinium 157.25(3) 1
31 Ga Gallium 69.723(1)
32 Ge Germanium 72.630(8)
79 Au Gold 196.966 570(4)
72 Hf Hafnium 178.49(2)
108 Hs Hassium [270] 4
2 He Helium 4.002 602(2) 1, 2
67 Ho Holmium 164.930 328(7)
1 H Hydrogen 1.008 3, 5
49 In Indium 114.818(1)
53 I Iodine 126.904 47(3)
77 Ir Iridium 192.217(2)
26 Fe Iron 55.845(2)
36 Kr Krypton 83.798(2) 1, 3
57 La Lanthanum 138.905 47(7) 1
103 Lr Lawrencium [262] 4
82 Pb Lead 207.2(1) 1, 2
3 Li Lithium 6.94 3, 5
116 Lv Livermorium [293] 4
71 Lu Lutetium 174.9668(1) 1
12 Mg Magnesium 24.305 5
25 Mn Manganese 54.938 043(2)
109 Mt Meitnerium [278] 4
101 Md Mendelevium [258] 4
80 Hg Mercury 200.592(3)
42 Mo Molybdenum 95.95(1) 1
115 Mc Moscovium [289] 4
60 Nd Neodymium 144.242(3) 1
10 Ne Neon 20.1797(6) 1, 3
93 Np Neptunium [237] 4
28 Ni Nickel 58.6934(4)
113 Nh Nihonium [286] 4
41 Nb Niobium 92.906 37(1)
7 N Nitrogen 14.007 5
102 No Nobelium [259] 4
118 Og Oganesson [294] 4
76 Os Osmium 190.23(3) 1
8 O Oxygen 15.999 5
46 Pd Palladium 106.42(1) 1
15 P Phosphorus 30.973 761 998(5)
78 Pt Platinum 195.084(9)
94 Pu Plutonium [244] 4
84 Po Polonium [209] 4
19 K Potassium 39.0983(1)
59 Pr Praseodymium     140.907 66(1)
61 Pm Promethium [145] 4
91 Pa Protactinium 231.035 88(1) 4
88 Ra Radium [226] 4
86 Rn Radon [222] 4
75 Re Rhenium 186.207(1)
45 Rh Rhodium 102.905 49(2)
111 Rg Roentgenium [281] 4
37 Rb Rubidium 85.4678(3) 1
44 Ru Ruthenium 101.07(2) 1
104 Rf Rutherfordium [267] 4
62 Sm Samarium 150.36(2) 1
21 Sc Scandium 44.955 908(5)
106 Sg Seaborgium [269] 4
34 Se Selenium 78.971(8)
14 Si Silicon 28.085 5
47 Ag Silver 107.8682(2) 1
11 Na Sodium 22.989 769 28(2)    
38 Sr Strontium 87.62(1) 1, 2
16 S Sulfur 32.06 5
73 Ta Tantalum 180.947 88(2)
43 Tc Technetium [97] 4
52 Te Tellurium 127.60(3) 1
117 Ts Tennessine [293] 4
65 Tb Terbium 158.925 354(8)
81 Tl Thallium 204.38 5
90 Th Thorium 232.0377(4) 1, 4
69 Tm Thulium 168.934 218(6)
50 Sn Tin 118.710(7) 1
22 Ti Titanium 47.867(1)
74 W Tungsten 183.84(1)
92 U Uranium 238.028 91(3) 1, 3, 4
23 V Vanadium 50.9415(1)
54 Xe Xenon 131.293(6) 1, 3
70 Yb Ytterbium 173.045(10) 1
39 Y Yttrium 88.905 84(1)
30 Zn Zinc 65.38(2) 2
40 Zr Zirconium 91.224(2) 1

It’s Elemental

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