Periodic Table of Elements




Calcium was first discovered by Sir Humphry Davy, a British Chemist, in 1808, in England, through the electrolysis of a mixture of lime (CaO) and mercuric oxide (HgO).

Name: Calcium
Symbol: Ca
Atomic number: 20
Atomic weight: 40.078
State: solid
Group, period, block: 2, 4, s
Color: dull gray, silver
Classification: alkaline earth metal
Electron configuration: 4s2

Physical properties

Density: 1.55 g/cm-3
Melting point: 1115 K, 842 C, 1548 F
Boiling point: 1757 K, 1484 C, 2703 F

Atomic properties

Oxidation states: +2, +1[1]
Electronegativity: 1.00 (Pauling scale)
Ionization energies: 1st: 589.8 kJmol-1
Covalent radius: 17610 pm
Van der Waals radius: 231 pm
  • Ca
  • Electron Configuration


There are six naturally occurring isotopes of calcium exist, 40Ca, 42Ca, 43Ca, 44Ca, 46Ca and 48Ca.