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Strontium

What is Strontium

Strontium (pronunciation: STRON-she-em) is a soft, silvery element that belongs to the family of alkali earth metals and is represented by the chemical symbol Sr [1, 2]. Being chemically highly reactive, it reacts with water and burns in the air [1, 3].

Strontium

Isotopes

Strontium is characterized by four naturally occurring isotopes, including 84Sr, 86Sr, 87Sr, and 88Sr, all of which are stable [4]. In addition to these four isotopes, more than 30 unstable isotopes exist, out of which the longest-lived are 85Sr and 90Sr with half-lives of 64.853 days and 28.9 years respectively [5].

Where is Strontium Found

Strontium is mainly obtained from the mineral ores strontianite (SrCO3) and celestite (SrSO4) [1, 6]. It is commercially produced through reduction of strontium oxide (SrO) with aluminum, or through electrolysis of the molten mixture of potassium chloride and strontium chloride [1]. Today, the leading producers of strontium are China, Spain, and Mexico while the top reserve holding country is China [1].

History

Origin of its Name: It is named after the small Scottish town Strontian [1].

Who discovered it: The element was first found by the Northern Irish physicist and chemist Adair Crawford [1].

When and How was it Discovered

In 1787, Adair Crawford analyzed an unusual rock that he found in a mine at Strontian [1]. He named the new mineral, which consisted of an unknown element, strontia [1]. A Scottish chemist, Thomas Charles Hope, investigated the element in 1791 and found that it causes the candle flame to burn red [1]. At the same time, Martin Heinrich Klaproth independently worked with the mineral in Germany and successfully produced both oxide and hydroxide of strontium [1].

In 1808, Sir Humphry Davy isolated strontium metal through electrolysis of a molten salt of strontium sulfate [6]. He used mercury and platinum as negative and positive electrodes respectively [6].

Strontium Symbol

Strontium Identification

Atomic number 38 [1]
CAS number 7440-24-6 [1]
Position in the periodic table Group Period Block
  2 [1] 5 [1] s [1]

Properties and Characteristics of Strontium

General Properties

Relative atomic mass 87.62 [1]
Atomic mass 87.62 amu [1]
Molar mass 87.6200 g/mol [7]

Physical Properties

Color Silvery [1, 6]
Melting point/freezing point 777 °C, 1431 °F [1]
Boiling point 1377 °C, 2511 °F [1]
Density 2.64 g cm-3 [1]
State of matter at room temperature (solid/liquid/gas) Solid [1, 6]
Hardness
– Brinell Unknown [8]
– Mohs 1.5 [8]
– Vickers Unknown [8]
Electrical Conductivity 7.7 X 106 S/m [8]
Charge  +2 [9]
Thermal (heat) conductivity 35 W/(m K) [8]
Specific heat 306 J kg-1 K-1 [1]
Bulk modulus Unknown [1]
Shear modulus Unknown [1]
Young’s modulus Unknown [1]
Vapor pressure
– Temperature (K) 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
– Pressure (Pa) 4.99X 10-11 4.29X 10-4 1.134 121

Chemical Properties

Oxidation states 2 [1]
Isotopes Isotope Mass Abundance (%) Half-life Mode of decay
  84Sr 83.913 0.56
  86Sr 85.909 9.86
  87Sr 86.909 7
  88Sr 87.906 82.58

Strontium Lewis Dot Structure

Atomic Data of Strontium (Element 38)

Valence electrons 2 [10]
Quantum numbers
– n 5 [10]
– ℓ 0 [10]
– m 0 [10]
– ms -1/2 [10]
Electron configuration (noble gas configuration) [Kr] 5s2 [1]
Atomic structure
– Number of electrons 38 [6]
– Number of neutrons 50 [6]
– Number of protons 38 [6]
Radius of Atom
– Atomic radius 2.49 Å [1]
– Covalent radius 1.90 Å [1]
Electronegativity (Pauling-scale) 0.95 [1]
Electron affinity 4.631 [1]
Ionization energy (kJ mol-1) 1st 2nd 3rd 4th 5th 6th 7th 8th
  549.47 1064.243 4138.26 5500 6908.4 8760.9 10227 11800.2

Strontium Electron Configuration (Bohr Model)

What is it Used for

  • Strontium salts are known to produce brilliant red color and are commonly added to firework mixtures and road flares [1, 3].
  • It is used in ferrite magnets production and zinc refining processes [3].
  • Strontium aluminate and strontium carbonate are used in ‘glow-in-the-dark’ plastics and paints in which the light absorbed during the day are slowly released afterward [1].
  • The radioactive isotope Strontium-90 is a high-energy beta emitter and can be used for generating electricity in remote weather stations, navigation buoys, and space vehicles [1, 3].
  • Strontium-90 can as well be used for removing static charges from machinery that handles plastic or paper [1].
  • Strontium chloride along with strontium acetate, used as an ingredient in toothpaste, helps in relieving pain caused by sensitive teeth [11].
  • Research indicates that intravenous Strontium-89 chloride can be used for reducing pain associated with metastatic bone cancer [11].

Toxicity of Strontium

Some deep-sea creatures incorporate strontium into their shells, and thus the element is necessary for some stony corals [1]. Like calcium, it can be absorbed by human bones, but is not harmful and does not play any biological role in our body [1]. Exposure to radioactive 90Sr, an extremely hazardous component in the fallout from nuclear power plant accidents and nuclear explosions, can increase the risks of developing cancers of blood, nose, lung, and the bone [1, 3, 12].

Strontium Element 38

Interesting Facts

  • Strontium is a common element in nature and is 15th most abundant in Earth’s crust [3].
  • When it reacts with water, it produces strontium hydroxide, which is a severe respiratory, skin and eye irritant [3].
  • The element is graphically represented by an abstract image of a metallic mushroom cloud, indicating its presence in nuclear fallout [1].

Cost of Strontium

The price of pure strontium is about $1 per gram [6].

References

  1. http://www.rsc.org/periodic-table/element/38/strontium
  2. https://education.jlab.org/itselemental/ele038.html
  3. https://www.livescience.com/34522-strontium.html
  4. https://wwwrcamnl.wr.usgs.gov/isoig/period/sr_iig.html
  5. https://education.jlab.org/itselemental/iso038.html
  6. https://www.chemicool.com/elements/strontium.html
  7. https://www.webqc.org/molecular-weight-of-Strontium.html
  8. http://periodictable.com/Elements/038/data.html
  9. https://pubchem.ncbi.nlm.nih.gov/compound/strontium_ion#section=Top
  10. http://chemistry-reference.com/q_elements.asp?Symbol=Sr&language=en
  11. https://www.webmd.com/vitamins/ai/ingredientmono-1077/strontium
  12. http://www.dhss.delaware.gov/dph/files/strontiumfaq.pdf

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