Calcium

Calcium is the chemical element wi seembol Ca an atomic nummer 20. Calcium is a saft gray alkaline yird metal, an is the fift-maist-abundant element bi mass in the Yird's crust. Calcium is the fift-maist-abundant dissolved ion in seawatter bi baith molarity an mass, efter sodium, chloride, magnesium, an sulphate.^[5]

Calcium, ₂₀Ca

Calcium
Appearance	dull gray, siller; wi a pale yellae tint[1]
Standard atomic weight Ar, std(Ca)	7001400780000000000♠40.078(4)[2]
Calcium in the periodic cairt
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 Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) 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 Gowd Mercur (element) Thallium Leid (element) 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 Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium Mg ↑ Ca ↓ Sr potassium ← calcium → scandium
Atomic nummer (Z)	20
Group	group 2 (alkaline yird metals)
Period	period 4
Block	s-block
Element category	Alkaline yird metal
Electron confeeguration	[Ar] 4s2
Electrons per shell	2, 8, 8, 2
Pheesical properties
Phase at STP	solit
Meltin pynt	1115 K ​(842 °C, ​1548 °F)
Bylin pynt	1757 K ​(1484 °C, ​2703 °F)
Density (near r.t.)	1.55 g/cm3
when liquid (at m.p.)	1.378 g/cm3
Heat o fusion	8.54 kJ/mol
Heat o vapourisation	154.7 kJ/mol
Molar heat capacity	25.929 J/(mol·K)
Vapour pressur 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 strangly basic
Electronegativity	Pauling scale: 1.00
Ionisation energies	1st: 589.8 kJ/mol 2nd: 1145.4 kJ/mol 3rd: 4912.4 kJ/mol (more)
Atomic radius	empirical: 197 pm
Covalent radius	176±10 pm
Van der Waals radius	231 pm
Colour lines in a spectral range Spectral lines o calcium
Ither properties
Naitural occurrence	primordial
Creestal structur	​face-centred cubic [[File:face-centred cubic|frameless|alt=Face-centred cubic creestal structur for calcium|upright=0.23|Face-centred cubic creestal structur for calcium]]
Speed o soond thin rod	3810 m/s (at 20 °C)
Thermal expansion	22.3 µm/(m·K) (at 25 °C)
Thermal conductivity	201 W/(m·K)
Electrical resistivity	33.6 nΩ·m (at 20 °C)
Magnetic orderin	diamagnetic
Magnetic susceptibility	+40.0·10−6 cm3/mol[4]
Young's modulus	20 GPa
Shear modulus	7.4 GPa
Bulk modulus	17 GPa
Poisson ratio	0.31
Mohs haurdness	1.75
Brinell haurdness	170–416 MPa
CAS Nummer	7440-70-2
History
Diskivery an first isolation	Humphry Davy (1808)
Main isotopes o calcium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct 40Ca 96.941% stable 41Ca trace 9.94×104 y ε 41K 42Ca 0.647% stable 43Ca 0.135% stable 44Ca 2.086% stable 45Ca syn 162.6 d β− 45Sc 46Ca 0.004% stable 47Ca syn 4.5 d β− 47Sc γ – 48Ca 0.187% 6.4×1019 y β−β− 48Ti
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Calcium is essential for livin organisms, in parteecular in cell pheesiology, whaur muivement o the calcium ion Ca²⁺ intae an oot o the cytoplasm functions as a signal for mony cellular processes. As a major material uised in mineralisation o bane, teeth an shells, calcium is the maist abundant metal bi mass in mony ainimals.