Strontium

Strontium, ₃₈Sr

Strontium
Pronunciation	/ˈstrɒntiəm/ (STRON-tee-əm) /ˈstrɒnʃiəm/ (STRON-shee-əm)
Appearance	silvery white metallic; with a pale yellow tint[1]
Standard atomic weight Ar°(Sr)
	87.62±0.01[2] 87.62±0.01 (abridged)[3]
Strontium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Ca ↑ Sr ↓ Ba rubidium ← strontium → yttrium
Atomic number (Z)	38
Group	group 2 (alkaline earth metals)
Period	period 5
Block	s-block
Electron configuration	[Kr] 5s2
Electrons per shell	2, 8, 18, 8, 2[4]
Physical properties
Phase at STP	solid
Melting point	1050 K ​(777 °C, ​1431 °F)
Boiling point	1650 K ​(1377 °C, ​2511 °F)
Density (at 20° C)	2.582 g/cm3[5]
when liquid (at m.p.)	2.375 g/cm3
Heat of fusion	7.43 kJ/mol
Heat of vaporization	141 kJ/mol
Molar heat capacity	26.4 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 796 882 990 1139 1345 1646
Atomic properties
Oxidation states	common: +2 +1[6]
Electronegativity	Pauling scale: 0.95
Ionization energies	1st: 549.5 kJ/mol 2nd: 1064.2 kJ/mol 3rd: 4138 kJ/mol
Atomic radius	empirical: 215 pm
Covalent radius	195±10 pm
Van der Waals radius	249 pm
Spectral lines of strontium
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered cubic (fcc) (cF4)
Lattice constant	a = 608.6 pm (at 20 °C)[5]
Thermal expansion	22.55×10−6/K (at 20 °C)[5]
Thermal conductivity	35.4 W/(m⋅K)
Electrical resistivity	132 nΩ⋅m (at 20 °C)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	−92.0×10−6 cm3/mol (298 K)[7]
Young's modulus	15.7 GPa
Shear modulus	6.03 GPa
Poisson ratio	0.28
Mohs hardness	1.5
CAS Number	7440-24-6
History
Naming	after the mineral strontianite, itself named after Strontian, Scotland
Discovery	William Cruickshank (1787)
First isolation	Humphry Davy (1808)
Isotopes of strontium v e
Main isotopes[8] Decay abun­dance half-life (t1/2) mode pro­duct 82Sr synth 25.36 d ε 82Rb 83Sr synth 1.35 d ε 83Rb β+ 83Rb γ – 84Sr 0.56% stable 85Sr synth 64.84 d ε 85Rb γ – 86Sr 9.86% stable 87Sr 7% stable 88Sr 82.6% stable 89Sr synth 50.52 d β− 89Y 90Sr trace 28.90 y β− 90Y
Category: Strontium view talk edit | references

Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to air. Strontium has physical and chemical properties similar to those of its two vertical neighbors in the periodic table, calcium and barium. It occurs naturally mainly in the minerals celestine and strontianite, and is mostly mined from these.

Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was discovered in 1790 by Adair Crawford and William Cruickshank; it was identified as a new element the next year from its crimson-red flame test color. Strontium was first isolated as a metal in 1808 by Humphry Davy using the then newly discovered process of electrolysis. During the 19th century, strontium was mostly used in the production of sugar from sugar beets (see strontian process). At the peak of production of television cathode-ray tubes, as much as 75% of strontium consumption in the United States was used for the faceplate glass.^[9] With the replacement of cathode-ray tubes with other display methods, consumption of strontium has dramatically declined.^[9]

While natural strontium (which is mostly the isotope strontium-88) is stable, the synthetic strontium-90 is radioactive and is one of the most dangerous components of nuclear fallout, as strontium is absorbed by the body in a similar manner to calcium. Natural stable strontium, on the other hand, is not hazardous to health.