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Chemical element with atomic number 20 (Ca)
Calcium, 20Ca
Crystals of silvery calcium metal in a glass vial
Calcium
Appearancedull gray, silver; with a pale yellow tint[1]
Standard atomic weight Ar°(Ca)
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
Atomic number (Z)20
Group group 2 (alkaline earth metals)
Period period 4
Block   s-block
Electron configuration [Ar] 4s2
Electrons per shell2, 8, 8, 2
Physical properties
Phase at STP solid
Melting point 1115 K ​(842 °C, ​1548 °F)
Boiling point 1757 K ​(1484 °C, ​2703 °F)
Density (at 20° C)1.526 g/cm3 [4]
when liquid (at m.p.)1.378 g/cm3
Heat of fusion 8.54 kJ/mol
Heat of vaporization 154.7 kJ/mol
Molar heat capacity 25.929 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 common: +2
+1[5]
Electronegativity Pauling scale: 1.00
Ionization 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
Color lines in a spectral range
Spectral lines of calcium
Other properties
Natural occurrenceprimordial
Crystal structure ​face-centered cubic (fcc) (cF4)
Lattice constant a = 558.8 pm (at 20 °C)[4]
Thermal expansion 22.27×ばつ10−6/K (at 20 °C)[4]
Thermal conductivity 201 W/(m⋅K)
Electrical resistivity 33.6 nΩ⋅m (at 20 °C)
Magnetic ordering diamagnetic
Molar magnetic susceptibility +40.0×ばつ10−6 cm3/mol[7]
Young's modulus 20 GPa
Shear modulus 7.4 GPa
Bulk modulus 17 GPa
Speed of sound thin rod3810 m/s (at 20 °C)
Poisson ratio 0.31
Mohs hardness 1.75
Brinell hardness 170–416 MPa
CAS Number 7440-70-2
History
Naming from the Latin word for lime, calx
Discovery and first isolationHumphry Davy (1808)
Isotopes of calcium
Main isotopes[8] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
40Ca 96.9% stable
41Ca trace 9.94×ばつ104 y ε 41K
42Ca 0.647% stable
43Ca 0.135% stable
44Ca 2.09% stable
45Ca synth 162.61 d β− 45Sc
46Ca 0.004% stable
47Ca synth 4.536 d β− 47Sc
48Ca 0.187% 5.6×ばつ1019 y β−β− 48Ti
 Category: Calcium
| references
  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
  2. ^ "Standard Atomic Weights: Calcium". CIAAW. 1983.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022年05月04日). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ^ a b c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  5. ^ Calcium(I) has been obtained as a dinuclear organometallic complex with an arene dianion, see Krieck, Sven; Görls, Helmar; Yu, Lian; Reiher, Markus; Westerhausen, Matthias (2009). "Stable "Inverse" Sandwich Complex with Unprecedented Organocalcium(I): Crystal Structures of [(thf)2Mg(Br)-C6H2-2,4,6-Ph3] and [(thf)3Ca{μ-C6H3-1,3,5-Ph3}Ca(thf)3]". Journal of the American Chemical Society. 131 (8): 2977–2985. doi:10.1021/ja808524y..
  6. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
  7. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  8. ^ 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.

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