Atomic #-  38

Atomic Weight- 87.62

Electron Configuration - 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s^{2        
   (}the two electrons in the highest energy level 3s² give Strontium its ionic charge of    +2)

Intensive Physical Properties -
            Boiling Point (K)- 1650
            Melting Point (K)- 1041
            Density (g/cm³)- 2.6
           
Electronegativity - (Pauling's Scale) - .95

Atomic Radius Of Free Atom - 2.45A

        

Physical Properties

Strontium is a lightweight, silvery-white metal. It is less dense than Calcium and is not found free in nature.  Strontium is silver-white when freshly cut but rapidly turns a yellowish color through oxidation.

Common Chemical Reactions

Strontium, like Magnesium, forms and oxide layer (giving Strontium its yellowish color) .  Once ignited, Strontium burns with a bright white flame and form an oxide (SrO) and a nitride (Sr₃O₂)

           The surface layer of Sr reacts with Oxygen and Nitrogen in the air to form  an oxide that protects it from corrosion

          2Sr(s) + O₂(g) 2SrO(s)

          3Sr(s) + N₂(g) Sr₃N₂(s)

             When placed in water, Strontium sinks to the bottom and then begins to react with the water.  Small bubbles of H₂ appear on the surface.  Sr reacts quicker than Ca but slower than Ba

            Sr(s) + 2H₂O(g) Sr(OH)₂(aq) + H₂(g)

             Strontium is very reactive towards the halogens such as chlorine, Cl₂ or bromine, Br₂, and Iodine, I₂. and burns (reacts) to form the dihalides strontium(II) chloride, MgCl₂ and strontium(II) bromide, MgBr₂, respectively.  These reactions occur around 400 C^o

            Sr(s) + Cl₂(g) SrCl₂(s)

            Sr(s) + Br₂(g) SrBr₂(s)

            Sr(s) + I₂(g) SrI₂(s)

A Few Isotopes
Taken from Web Elements

     Ex:   ⁸⁹Sr has a half life of 52.50 days

Strontium⁹⁰ has a half life of 29 years and is a part of nuclear fallout.

Sources of Strontium

Strontium is never found as a free element in nature. Like other Alkaline metals, it readily combines with other elements

Strontium can be found in minerals such as Celestite  and Strontianite

Uses of Strontium

• used in flares and pyrotechnics.  As a salt, Strontium burns several different colors...primarily red (see right
• In compounds, Strontium is used in optical materials, especially Television tubes
• As Strontium titanate, it has higher optical dispersion than a diamond and has been used in the production of gemstones
• Strontium⁹⁰ can be used in lightweight nuclear reactions to produce electricity

Strontium in Biology

Strontium has no positive role in biology.  However, because it chemically resembles Calcium it can be found bones where Calcium should be.  The same occurs with ⁹⁰Sr which was a radioactive product of nuclear testing during the 1950s

Excess= bone degradation

Deficiency= no side effects

History of Strontium

Adair Crawford in 1790 recognized a new mineral (strontianite) in samples of witherite (a mineral consisting of barium carbonate, BaCO₃) from Scotland. It was some time before it was recognized that strontianite contained a new element. Strontianite is now known to consists of strontium carbonate, SrCO₃. The element itself was not isolated for a number of years after this when strontium metal was isolated by Davy by electrolysis of a mixture containing strontium chloride and mercuric oxide in 1808.

Discovered by: Adair Crawford
Isolated By: Sir Humphrey Davey (1808)
Discovered in: Scotland
Discovered When: 1790