20 Ca Calcium 40.078 u

Calcium

Period
4
Group
2
Block
s-block
Phase (STP)
Solid

Calcium is the most abundant metal in the human body. It is essential for bones, teeth, and cellular signaling.

Appearance: Dull gray, silver

About Calcium

Calcium is an alkaline earth metal of atomic number 20 and atomic mass 40.078, a dull gray solid that melts at 1115 K. Two valence electrons ([Ar] 4s2) give it an electronegativity of 1.00 and a first ionization energy of 590 kJ/mol, and it readily forms a doubly charged ion. Humphry Davy isolated the metal in 1808. Calcium is the most abundant metal in the human body, providing the structural mineral of bones and teeth and serving as a signaling ion within cells. In nature it occurs in minerals rather than as the free metal. The element sits in group 2, period 4, below magnesium.

Physical Properties

Atomic Mass 40.078 u
Density 1.55 g/cm³
Melting Point 841.9 °C
Boiling Point 1483.8 °C
Phase at STP Solid
Atomic Radius 194.0 pm

Electronic Properties

Electronegativity 1.0
Ionization Energy 589.8 eV
Electron Affinity 2.37 eV
Valence Electrons 2

Electron Configuration

Configuration [Ar] 4s²

Electron Shell Configuration

Calcium electron shell configuration Ca 2e⁻ 8e⁻ 8e⁻ 2e⁻
Electron shell structure of Calcium — electrons per shell.
Shell Electrons
1 (K) 2
2 (L) 8
3 (M) 8
4 (N) 2

Position in Periodic Table

Calcium position in the periodic table Ca

Discovery

Discovered by: Humphry Davy
Year: 1808

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

Reactions Involving Ca

Decomposition of Calcium Carbonate (Calcination)

CaCO₃ → CaO + CO₂

Decomposition

Beta Decay of Potassium-40

⁴⁰K → ⁴⁰Ca + e⁻ + ν̄ₑ

Nuclear

Calcium Carbonate and Hydrochloric Acid

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Double Replacement

Calcium Carbonate and Hydrochloric Acid (Antacid)

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Acid-Base

Calcium Carbonate Precipitation

CaCl₂ + Na₂CO₃ → CaCO₃↓ + 2NaCl

Precipitation
View all 18 reactions →

Compounds Containing Calcium

Calcium Acetate

Ca(C₂H₃O₂)₂

Calcium Aluminate Cement

CaO·Al₂O₃

Calcium Carbonate

CaCO₃

Calcium Chloride

CaCl₂

Calcium Citrate

Ca₃(C₆H₅O₇)₂

Calcium Fluoride

CaF₂

Calcium Hydride

CaH₂

Calcium Hydroxide

Ca(OH)₂

Calcium Hypochlorite

Ca(OCl)₂

Calcium Oxide

CaO

Calcium Phosphate

Ca₃(PO₄)₂

Calcium Propionate

Ca(C₂H₅COO)₂

More Alkaline Earth Metal

4 Be Beryllium 12 Mg Magnesium 38 Sr Strontium 56 Ba Barium 88 Ra Radium

Explore on Science FYI

MineralFYI
Calcite

Calcium carbonate — primary limestone mineral

Frequently Asked Questions

What is Calcium?
Calcium (Ca) is a chemical element with atomic number 20. It is a solid at standard temperature and pressure, classified as a alkaline earth metal.
What are the key properties of Calcium?
Calcium has an atomic mass of 40.078 u, density of 1.55 g/cm³, melting point of 841.9°C, boiling point of 1483.8°C.
What is the electron configuration of Calcium?
The electron configuration of Calcium is [Ar] 4s2. It is in the s-block of the periodic table.
Who discovered Calcium?
Calcium was discovered by Humphry Davy in 1808.
What is the electronegativity of Calcium?
Calcium has an electronegativity of 1.0 on the Pauling scale.