About

Strontium is a soft, silvery-white alkaline earth metal that turns yellow when exposed to air. It is best known for the brilliant crimson color its salts impart to flames, making it a common ingredient in fireworks, emergency signal flares, and military tracer ammunition. The radioactive isotope strontium-90 is a hazardous component of nuclear fallout.

Atomic Properties

Atomic Number38

Atomic Weight87.62 u

Neutrons (common)50

Electron Configuration[Kr] 5s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s²

Electrons per Shell2, 8, 18, 8, 2

Electronegativity0.95

Electron Affinity5.03 kJ/mol

Oxidation States+2

Covalent Radius195 pm

Van der Waals Radius249 pm

Ionic Radius118 pm

Periodic Table Position

Group2

Period5

BlockS

Chemical SeriesAlkaline earth metals

Physical Properties

State at STPsolid

Appearancesilvery white metallic, turns yellow on exposure to air

Crystal Structurefcc

Magnetic Orderingparamagnetic

Speed of Sound1,800 m/s

Poisson Ratio0.28

Thermal Properties

Melting Point1,050 K

Boiling Point1,655 K

Triple Point1,050 K

Thermal Expansion0 1/K

Thermal Conductivity35.4 W/(m·K)

Specific Heat0.301 J/(g·K)

Molar Heat26.4 J/(mol·K)

Heat of Fusion7.43 kJ/mol

Heat of Vaporization144 kJ/mol

Abundance

In Earth's Crust370 ppm

In Ocean8.1 ppm

In Solar System0.02 ppm

In Human Body4.6 ppm

In Universe0.04 ppm

Discovery

Discovered byAdair Crawford

Discovery Year1,790

Occurrenceprimordial

CAS Number7440-24-6

Electron Configuration

Energy

↿⇂

Isotopes of Strontium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
⁸⁴Sr	83.913420	0.56%	Stable	Stable
⁸⁵Sr	84.912933	—	64.846 d	Electron Capture
⁸⁶Sr	85.909260	9.86%	Stable	Stable
⁸⁷Sr	86.908880	7%	Stable	Stable
⁸⁸Sr	87.905610	82.58%	Stable	Stable
⁹⁰Sr	89.907738	—	28.91 y	Beta Minus Decay

Interactive Visualization

Explore the 3D Bohr model of Strontium in our interactive viewer.

View 3D Model of Strontium