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Calcium (Ca)

From Wikipedia, the free encyclopediaCalcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust. The ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.

Calcium in the periodic table

Atomic number20
Element categoryAlkaline Earth Metal

Physical properties

Phase at STPSolid
Density1.55 g/cm3
Atomic weight40.0784 u
Melting point1115 K
841.85 °C
1547.33 °F
Boiling point1757 K
1483.85 °C
2702.93 °F

Atomic properties

Electronegativity (Pauling Scale)1
Electron affinity2.37 kJ/mol
Oxidation states+1, +2
(a strongly basic oxide)
Ionization energies
1589.8 kJ/mol
2 1145.4 kJ/mol
3 4912.4 kJ/mol
4 6491 kJ/mol
5 8153 kJ/mol
6 10496 kJ/mol
7 12270 kJ/mol
8 14206 kJ/mol
9 18191 kJ/mol
10 20385 kJ/mol
11 57110 kJ/mol
12 63410 kJ/mol
13 70110 kJ/mol
14 78890 kJ/mol
15 86310 kJ/mol
16 94000 kJ/mol
17 104900 kJ/mol
18 111711 kJ/mol
19 494850 kJ/mol
20 527762 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)[Ar] 4s2
Electron configuration1s2 2s2 2p6 3s2 3p6 4s2
Electrons per shell2, 8, 8, 2


Discovered byHumphry Davy
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