Calcium

Symbol: Ca
Atomic number: 20
Category: alkaline earth metals
Group: 2
Period: 4
Block: s
Atomic weight: 40.078 g/mol
Electrons per shell: 2, 8, 8, 2
CAS number: 7440-70-2
Phase: solid
Density: 1.55 kg/dm³ (near room temperature)
Melting point: 1115 K (842 °C, 1548 °F)
Boiling point: 1757 K (1484 °C, 2703 °F)
Crystal structure: face centered cubic
Oxidation states: 2
Electronegativity: 1.00 (Pauling scale)
Name's origin: calisis
Name's meaning: lime, as the Ancient Romans prepared lime as calcium oxide
Facts:
- is essential for living organisms, particularly in cell physiology
- is not naturally found in its elemental state, but occurs most commonly in sedimentary rocks in the minerals calcite, dolomite and gypsum
- is somewhat difficult to ignite, unlike magnesium, but when lit, the metal burns in air with a brilliant high-intensity red light
- calcium metal reacts with water, evolving hydrogen gas at a rate rapid enough to be noticeable