#38 / 118
38Sr87.62
Alkaline Earth Metalssolid at STPS-block

Strontium

Group: 2Period: 5Standard Atomic Weight: 87.62 u

Why is Strontium in this position?

Understanding the scientific rationale behind Strontium's position in the periodic table:

Group Assignment
Group 2

Belongs to Group 2 because it has 2 valence electrons in its outer 5s orbital (5s²).

Period Assignment
Period 5

Belongs to Period 5 because its outermost electrons occupy principal shell n=5.

Orbital Block
S-block

Belongs to the s-block because the differentiating electrons enter the 5s subshell.

Chemical Category
Alkaline Earth Metals

Classified as an alkaline earth metal due to basic oxide formation and stable +2 oxidation states.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 8, 2]

Bohr Atomic Shell Model(2, 8, 18, 8, 2)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

38 Protons (p⁺)50 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 8Shell N: Electron 2 of 8Shell N: Electron 3 of 8Shell N: Electron 4 of 8Shell N: Electron 5 of 8Shell N: Electron 6 of 8Shell N: Electron 7 of 8Shell N: Electron 8 of 8OShell O: Electron 1 of 2Shell O: Electron 2 of 2SrZ = 38

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):8 / 32 electrons (25%)
Shell O (n=5):2 / 50 electrons (4%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s²

Neutral ground state configuration. Valence electrons: 2.

Atomic & Quantum Properties

Electronegativity (Pauling)0.95 Pauling
1st Ionization Energy549.5 kJ/mol
Electron Affinity-5.03 kJ/mol
Atomic Radius (empirical)219 pm
Common Oxidation States+2
Crystal StructureFCC

Physical & Thermal Properties

Density at STP2.64 g/cm³
Melting Point777 °C (1050 K)
Boiling Point1382 °C (1655 K)
Magnetic OrderingParamagnetic
Discovery Year1790
Discovered ByAdair Crawford

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Crimson-red fireworks, emergency flares, and signal munitions (Sr(NO₃)₂)
  • Ultra-precise strontium optical lattice atomic clocks (accurate to 1 second in 15 billion years)
  • Ferrite permanent ceramic magnets in loudspeaker drivers
  • Toothpaste formulations for sensitive teeth (Strontium chloride)
Occurrence in Nature

Found primarily in celestite (SrSO₄) and strontianite (SrCO₃) mineral ores.

Etymology & Name Origin

Named after the village of Strontian in the Scottish Highlands

Important Chemical Compounds
Sr(NO₃)₂ (Strontium nitrate)
SrCO₃ (Strontium carbonate)
SrTiO₃ (Strontium titanate / Fabulite)
SrCl₂ (Strontium chloride)
Interesting Chemical Facts
  • Modern strontium optical lattice clocks are so precise they can detect gravitational time dilation from elevating a clock by just 2 centimeters.
  • The radioactive isotope Strontium-90 (⁹⁰Sr, half-life 28.9 years) is a hazardous byproduct of nuclear fission that mimics calcium, depositing in bones and bone marrow.
  • Celestite crystals of strontium sulfate often form breathtaking pale-blue geodes up to several feet across.
Safety & Handling Note

Stable natural strontium is non-toxic, but radioactive Strontium-90 causes bone leukemia and osteosarcoma.