Calcium

Element 20 on the periodic table, symbol Ca, group 2, period 4.

Calcium 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.

Properties

Atomic Number: 20
Atomic Mass: 40.0784 u
Group: 2
Period: 4
Block: s-block
Category: Alkaline Earth Metal
State at 25 °C: Solid
Melting Point: 1,115 K · 841.9 °C
Boiling Point: 1,757 K · 1,483.9 °C
Density: 1.55 g/cm³
Atomic Radius: 180 pm
Electronegativity: 1
Oxidation States: +2
Abundance in Crust: 4.15e+4 mg/kg
Discovered: 1808
Discovered By: Humphry Davy

Electron Configuration

[Ar] 4s2

1s2 2s2 2p6 3s2 3p6 4s2

Ionisation Energies (kJ/mol)

1. 589.8
2. 1,145.4
3. 4,912.4
4. 6,491
5. 8,153
6. 10,496
7. 12,270
8. 14,206

Elements near Calcium

Elements in the same group share the number of outer electrons and behave in similar ways. Elements in the same period share a shell, so they change steadily from left to right.