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Calcium

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Calcium, 00Ca
BERJAYA
Calcium
Appearancedull gray, silver; with a pale yellow tint[1]
Standard atomic weight Ar°(Ca)
40.078(4)[2]
Calcium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
 Mg
↑
Ca
↓
Sr
potassium ← calcium → scandium
Groupgroup 2 (alkaline earth metals)
Periodperiod 4
Block  s-block
Electron configuration[Ar] 4s2
Electrons per shell2, 8, 8, 2
Physical properties
Phase at STPsolid
Melting point1115 K ​(842 °C, ​1548 °F)
Boiling point1757 K ​(1484 °C, ​2703 °F)
Density (near r.t.)1.55 g/cm3
when liquid (at m.p.)1.378 g/cm3
Heat of fusion8.54 kJ/mol
Heat of vaporization154.7 kJ/mol
Molar heat capacity25.929 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 864 956 1071 1227 1443 1755
Atomic properties
Oxidation states+1,[3] +2 (a strongly basic oxide)
ElectronegativityPauling scale: 1.00
Ionization energies
  • 1st: 589.8 kJ/mol
  • 2nd: 1145.4 kJ/mol
  • 3rd: 4912.4 kJ/mol
  • (more)
Atomic radiusempirical: 197 pm
Covalent radius176±10 pm
Van der Waals radius231 pm
Color lines in a spectral range
Spectral lines of calcium
Other properties
Natural occurrenceprimordial
Crystal structure ​face-centered cubic (fcc)
Face-centered cubic crystal structure for calcium
Speed of sound thin rod3810 m/s (at 20 °C)
Thermal expansion22.3 µm/(m⋅K) (at 25 °C)
Thermal conductivity201 W/(m⋅K)
Electrical resistivity33.6 nΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic
Molar magnetic susceptibility+40.0·10−6 cm3/mol[4]
Young's modulus20 GPa
Shear modulus7.4 GPa
Bulk modulus17 GPa
Poisson ratio0.31
Mohs hardness1.75
Brinell hardness170–416 MPa
CAS Number7440-70-2
History
Discovery and first isolationHumphry Davy (1808)
Isotopes of calcium
Main isotopes[5] Decay
abun­dance half-life (t1/2) mode pro­duct
40Ca 96.9% stable
41Ca trace 9.94×104 y ε 41K
42Ca 0.647% stable
43Ca 0.135% stable
44Ca 2.09% stable
45Ca synth 163 d β− 45Sc
46Ca 0.004% stable
47Ca synth 4.5 d β− 47Sc
48Ca 0.187% 6.4×1019 y β−β− 48Ti
BERJAYA Category: Calcium
| references
BERJAYA
Very pure calcium metal, not corroded
BERJAYA
Calcium metal in air, corroded

Calcium is a chemical element. Its symbol on the periodic table (a list of all the elements) is Ca. and its atomic number is 20.[6] The atomic number says where Calcium sits in the periodic table. It has 20 protons and 20 electrons (if is an atom, see ion). The most common isotopes are Ca-40 and Ca-44. Its mass number is about 40.07.[6]

Calcium is not found as a metal in the ground (a native element mineral) because it is too reactive.[7] Calcium carbonate, also known as calcite, is the most common calcium mineral.

Calcium is very important in the human body, for making bones and is an inorganic component found in bones, alongside phosphate.[8] 99% of calcium in the bone is stored in bones.[8] It is used in nerve and muscle (including the heart muscle) contraction. The name comes "calx", the Latin name for lime, or limestone.[6]

BERJAYA
Calcite

Properties

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Calcium is a soft white-gray opaque metal. It is solid at room temperature. The crystal structure of calcium metal changes between two allotropes, being face-centred cubic at room temperature and body-centred cubic above 464 °C (867 °F; 737 K).[9] It melts at 842 °C (1,548 °F; 1,115 K).

It does not conduct electricity as well as copper, but is much lighter in weight.[source?]

Chemistry

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Calcium metal burning

Calcium is the third alkaline earth metal, and has similar chemistry to the rest of the group. It is a strong reducing agent and base with two valence electrons.

Calcium metal reacts with oxygen in the air to make a layer of calcium oxide on the outside of the metal. This stops further chemical reactions (passivation) until the layer is removed. This compound is a strong Brønsted base and reacts with Brønsted acids to make calcium salts of the conjugate base.[source?] Non-passivated calcium metal can also make salts by reducing Brønsted acids directly to hydrogen gas.[source?] If the calcium salt of an acid is soluble in that acid or the solvent being used, the calcium-acid reaction is very fast and gives off a lot of heat.

Calcium compounds

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Calcium forms chemical compounds in the +2 oxidation state. Calcium compounds are colorless. Most calcium compounds are not toxic. They are needed in the human body, actually. They are unreactive as far as calcium ions go. Calcium oxide was used to make limelights, which have a flame heating calcium oxide and makes it glow very bright. Forms (compounds) of calcium include:

Isotopes of calcium

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Calcium has 6 naturally occurring isotopes (40Ca, 42Ca, 43Ca, 44Ca, 46Ca and 48Ca), of which 48Ca is very slightly radioactive with a half-life about 6.4×1019 years.[10] Traces of 41Ca, 45Ca and 47Ca are made by cosmic rays striking atoms, and are called cosmogenic nuclides. 41Ca is made by the neutron activation of 40Ca in the upper layers of the Earth's crust and has a half-life of 102,000 years. Since it decays to potassium-41, it is a critical indicator of solar system anomalies.

Calcium-40 is the most abundant isotope (96% of all natural calcium), since it comes from radiogenic 40K, which has a half-life of 1.25 billion years. However, along with calcium-46, it is theoretically unstable but with a half-life so long it has never been observed to decay.

Purpose and use

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Calcium is found in high amounts in soil, especially when the soil has been made from rocks high in the different calcium forms. It can be deposited into the soil over time by leaching and deposition. It comes from rainfall and leaching out of the atmosphere, and it probably plays a role in the water cycle (or rain cycle). Because calcium is so porous (which means water can go through it), the soil could use it on some layer as a natural filter. Leaching also causes calcium to go from the rain into human drinking water in some parts of the world, and causes "hard" drinking water, in places where there is a lot of calcium in the environment and water.

Humans

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When calcium is mixed into building materials in the right form and concentration, it makes buildings stronger and more resistant to weather. Calcium is used by humans in construction (as limestone, or calcium carbonate) to make concrete and bricks better for building with, and gypsum (calcium sulfate) as a plaster.[11]

In brewery (making alcohol) gypsum is used and is the good one. Gypsum (calcium sulphate) is the good mineral because it does not break down with boiling, which alcohol needs. Chalk (calcium bicarbonate) is the bad form to use in brewery because it does break down, deposits limescale on the equipment and brings out the "harsher characteristics" of the hops as well as its ions interacting negatively with the fermentation process.[12]

Humans (and other animals) use calcium to maintain or grow healthy bones and teeth.[13] Calcium is used in the body where electricity is used, like in the muscles and nerves. Calcium is useful for animals and humans, and is found in nature. Cow milk is rich in calcium and other nutrients so that baby cows drinking it from their mother can grow up healthy and strong.

Other uses

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As an element, calcium is used in the reduction of other metals. It can also be used to make alloys (metal mix) with other metals.

As chemical compounds

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BERJAYA
Concrete used to make a building

Calcium compounds are also important in chemistry. It is important for making things. It is a part of cement which is needed to make concrete (a hard substance that many buildings are made from.)

Calcium is part of calcium oxide. Calcium oxide is used to make paper, pottery, food, and to purify water (make it good to drink.) Calcium carbonate is used as a calcium supplement. Calcium permanganate can be used as a rocket propellant.

Calcium Supplements

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Calcium is used in supplements a lot to increase the size of the tablet (as a bulking agent), for example 500mg of calcium added to in vitamin D tablets[14] or other vitamin supplements. Usually it is in the form of calcium carbonate or calcium citrate. Calcium is added to some medications such as over-the-counter (OTC) antacid products (used to neutralize stomach acid). Calcium has the ability to neutralize stomach acid and some products (like Tums and Rolands, in America) have added calcium in the form of calcium carbonate.[15] The calcium content depends on the antacid product strength and can range from 270-400mg of calcium.[15]

Calcium supplements exist and taking less than 1,500mg a day is probably not going to cause harm.[13] Taking too much calcium in supplement form might damage the body, and a balanced, varied diet is usually enough to get all of the calcium the body needs. Supplements are taken with food.[16]

Some people have adverse reactions to calcium supplements, or more rarely, allergic reactions. Signs of adverse effects from calcium supplements (or hypercalcaemia) include feeling tired, confused, headache, an upset stomach (or tummy ache), constipation and throwing up.[16] Calcium can cause bone pain in high amounts or as an allergic or adverse reaction.[16].

Use in the body

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Calcium[17] as an element is not found in the human body, just calcium ions in the form of chemical compounds. In this form it is used in the body. People usually get enough calcium from the diet.[13] Adult humans (aged 19 to 64) need around 700mg of calcium daily.[13] Calcium is used throughout the human body,[13] used in most muscles. Taking 1,500mg of calcium (usually as a supplement in these amounts) is unlikely to cause harm.[13]

Dietary calcium comes from milk and dairy products or soya drinks with added calcium, fish where eating them includes the bones (for example, sardines), and green, leafy vegetables.[13] Vegetables that are high in calcium include curly kale and okra, but not spinach (which does contain a lot of calcium but it is not useful for the body).[13] Fortified flour which makes bread (called fortified food) might be a source of calcium or other the fortifying additives (such as niacin or vitamin B3) it contains.

Preparation

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Calcium metal is made by electrolysis, usually with melted calcium chloride in a molten salt bath. It has to be very hot to melt it. The reaction occurs in the range of 650 to 750 degrees celsius (C)[18] (around 1200 to 1560 degrees fahrenheit). Sometimes, additives are used to lower the boiling point of the metal. This is because pure calcium chloride melts at around 772 C, or calcium chloride melts in the range of 772 to 782 degrees celsius.[19]

Potassium chloride can be used as an additive for the preparation of calcium chloride via electrolysis. It make the extraction more efficient by lowering its boiling point. The amount of potassium added to the molten salt bath can range from 15 to 35 percent (with 75 percent calcium chloride), with 10 percent being the minimum or 25 percent being preferred.[18]

Safety

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Calcium is toxic as an element. It reacts with water and makes a strong base, calcium hydroxide. Calcium compounds are not toxic unless the anion is toxic. Calcium permanganate is only toxic because of the permanganate, not the calcium. Like other alkaline earth metals calcium burns easily and brightly.

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References

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  1. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112. ISBN 978-0-08-037941-8.
  2. ↑ "Standard Atomic Weights: Calcium". CIAAW. 1983.
  3. ↑ Krieck, Sven; Görls, Helmar; Westerhausen, Matthias (2010). "Mechanistic Elucidation of the Formation of the Inverse Ca(I) Sandwich Complex [(thf)3Ca(μ-C6H3-1,3,5-Ph3)Ca(thf)3] and Stability of Aryl-Substituted Phenylcalcium Complexes". Journal of the American Chemical Society. 132 (35): 12492–12501. doi:10.1021/ja105534w. PMID 20718434.
  4. ↑ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  5. ↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  6. 1 2 3 "Atomic Weight of Calcium | Commission on Isotopic Abundances and Atomic Weights". www.ciaaw.org. Retrieved 2026-04-09.
  7. ↑ "Calcium: the essentials". WebElements. Retrieved 7 February 2016.
  8. 1 2 Macnow, Alexander Stone; Kaplan Publishing, eds. (2024). MCAT Complete 7-book subject review 2025 -2026, set includes books, online prep, 3 ... practise tests. Fort Lauderdale, Florida: KAPLAN North America, LLC dba kaplan Publishing. ISBN 978-1-5062-9438-4.
  9. ↑ . doi:10.1149/1.2430364. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  10. ↑ Arnold, R.; et al. (NEMO-3 Collaboration) (2016). "Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of 48Ca with the NEMO-3 detector". Physical Review D. 93 (11): 112008. arXiv:1604.01710. Bibcode:2016PhRvD..93k2008A. doi:10.1103/PhysRevD.93.112008. S2CID 55485404.{{cite journal}}: CS1 maint: article number as page number (link)
  11. ↑ pubs.usgs.gov https://pubs.usgs.gov/sir/2017/5118/elements/Calcium/Ca_txt.html. Retrieved 2026-04-11. {{cite web}}: Missing or empty |title= (help)
  12. ↑ Bruning, Ted (2011). Home brewing: a guide to making your own beer, wine and cider. London: National Trust. ISBN 978-1-907892-03-5.
  13. 1 2 3 4 5 6 7 8 "Vitamins and minerals - Calcium". nhs.uk. 2017-10-23. Retrieved 2026-04-09.
  14. ↑ https://bnf.nice.org.uk/drugs/colecalciferol-with-calcium-carbonate/#:~:text=Prescribing%20and%20dispensing%20information%20For,details%20of%20other%20available%20products.
  15. 1 2 "Office of Dietary Supplements - Calcium". ods.od.nih.gov. Retrieved 2026-04-12.
  16. 1 2 3 "Calcium". drugs.com.{{cite web}}: CS1 maint: url-status (link)
  17. ↑ "MeSH Browser". meshb.nlm.nih.gov. Retrieved 2026-04-09.
  18. 1 2 US3226311A, Diest, Jacques Van, "Process of producing calcium by electrolysis", issued 1965-12-28
  19. ↑ PubChem. "Calcium Chloride". pubchem.ncbi.nlm.nih.gov. Retrieved 2026-04-09.


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