Atomic Element Z = 20 • Alkaline Earth Metal
Calcium (Ca) — Atomic Data, Electron Shells & Reactions
Calcium (symbol Ca, atomic number 20) has a standard atomic weight of 40.078 u and ground-state configuration [Ar] 4s2.
Atomic Number (Z)
20
IUPAC Symbol
Ca
Standard Atomic Weight
40.078 g/mol
Period / Group / Block
4 / 2 / s-block
Condensed Electron Config
[Ar] 4s2
Full Subshell Config
1s2 2s2 2p6 3s2 3p6 4s2
Principal Shell Occupancy
[2, 8, 8, 2]
Pauling Electronegativity
1
First Ionization Energy
590 kJ/mol
Covalent Radius
176 pm
Melting Point
1115 K (841.85 °C)
Boiling Point
1757 K (1483.85 °C)
Density
1.54 g/cm³
Oxidation States
+2
Ca (Z=20) — Valence shell highlighted in vermilion
Interactive Stoichiometry Reactions Involving Calcium:
H3PO4 + Ca(OH)2 -> Ca3(PO4)2 + H2O
AgNO3 + CaCl2 -> AgCl + Ca(NO3)2
CaC2 + H2O -> Ca(OH)2 + C2H2