Calcium

Symbol	Ca
Atomic number	20
Group	2 (Alkaline earth metal)
Period	4
Block	d
Classification	Alkaline Earth Metal

Appearance	-
Color	Silver

Number of protons	20 p+
Number of neutrons	20 n0
Number of electrons	20 e-

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.

Phase at STP	Solid
Density	1.55 g/cm3
Atomic weight	40.0784 u

Melting point	1115 K 841.85 °C 1547.33 °F
Boiling point	1757 K 1483.85 °C 2702.93 °F
Heat of vaporization	154.67 kJ/mol

Electronegativity (Pauling Scale)	1
Electron affinity	2.37 kJ/mol
Oxidation states	+1, +2 (a strongly basic oxide)
Ionization energies	589.8 kJ/mol 1145.4 kJ/mol 4912.4 kJ/mol 6491 kJ/mol 8153 kJ/mol 10496 kJ/mol 12270 kJ/mol 14206 kJ/mol 18191 kJ/mol 20385 kJ/mol 57110 kJ/mol 63410 kJ/mol 70110 kJ/mol 78890 kJ/mol 86310 kJ/mol 94000 kJ/mol 104900 kJ/mol 111711 kJ/mol 494850 kJ/mol 527762 kJ/mol

Electron configuration Shorthand configuration	[Ar] 4s2
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 4s2
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 4s2
Electrons per shell	2, 8, 8, 2
Valence electrons	2
Valency electrons	2
Bohr model	Figure: Shell diagram of Calcium (Ca) atom.
Orbital Diagram	1s 2s 2p 3s 3p 4s

Discovery and first isolation

Humphry Davy (1808)

Discovery of calcium Calcium compounds were known for millennia, although their chemical makeup was not understood until the 17th century. Lime as a building material and as plaster for statues was used as far back as around 7000 BC. Vitruvius, a Roman architect, noted that the lime that resulted was lighter than the original limestone, attributing this to the boiling of the water. In 1755, Joseph Black proved that this was due to the loss of carbon dioxide, which as a gas had not been recognised by the ancient Romans. In 1789, Antoine Lavoisier suspected that lime might be an oxide of a fundamental chemical element. Calcium, along with its congeners magnesium, strontium, and barium, was first isolated by Humphry Davy in 1808. Following the work of Jöns Jakob Berzelius and Magnus Martin af Pontin on electrolysis.

Original word	calx
Language of origin	Latin
Name source	Mineral
Meaning	“Lime”
Naming The name is derived from the Latin word 'calx' meaning lime, which was obtained from heating limestone.

CAS Number	7440-70-2
ChemSpider ID	4573905
EC number	231-179-5
PubChem CID Number	5460341