38
Sr
Strontium
87.62
Strontium (Sr)
Alkaline Earth MetalGroup 2Period 5s-block-block
Strontium is a chemical element with symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when it is exposed to air.
Latin name: Strontium
Atomic Number
38
Atomic Mass
87.62 g/mol
Phase (STP)
Solid
Electron Config.
[Kr] 5s²
General
SymbolSr
Atomic Number38
Atomic Mass87.62 g/mol
CategoryAlkaline Earth Metal
Group2
Period5
Blocks-block
Electron Configuration[Kr] 5s²
Valence Electrons2
Coloursilvery-yellow metallic
CAS NumberCAS7440-24-6
Physical Properties
Phase (STP)Solid
Density2.64 g/cm³
Melting Point776.85°C · 1430.33°F · 1050.00 K
Boiling Point1381.85°C · 2519.33°F · 1655.00 K
Atomic Properties
Atomic Radius219 pm
Electronegativity0.95 Pauling
Ionization Energy550 kJ/mol
Oxidation States+2
Ion ChargeSr2+
Thermodynamic
Molar Heat26.4 J/(mol·K)
Crystal Structure
Crystal Structureface-centered cubic
Mechanical Properties
Mohs Hardness1.5
Abundance
In Earth's Crust0.0400%
Discovery & History
Discovery Year1790
Discovered ByAdair Crawford
Country of DiscoveryScotland
Isotopes of Strontium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Sr-84 | 0.56% | Stable | — |
| Sr-86 | 9.86% | Stable | — |
| Sr-87 | 7% | Stable | — |
| Sr-88 | 82.58% | Stable | — |
| Sr-89 | — | 50.52 days | β⁻ |
| Sr-90 | — | 28.8 years | β⁻ |