From the Greek word Magnesia (a district of Thessaly)



Atomic #-  12

Atomic Weight- 24.305

Electron Configuration - 1s22s22p63s2        
the two electrons in the highest energy level 3s2 give Magnesium its ionic charge of    +2)

Intensive Physical Properties -
            Boiling Point (K)-
            Melting Point (K)- 922
            Density (g/cm3)- 1.74
Electronegativity -
(Pauling's Scale) - 1.31

Atomic Radius Of Free Atom -


Being an Alkaline Earth Metal, Magnesium forms a strong base when placed in water  (An Alkaline solution)  

Physical Properties

Magnesium is a lightweight, silvery-white metal. Finely divided Magnesium ignites readily and burns with a hot white flame.  Magnesium tarnishes slightly in air but is usually coated with a natural layer of MgO that protects it.

Common Chemical Reactions

There are a few compounds Magnesium forms readily:

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

          2Mg(s) + O2(g) 2MgO(s)

          3Mg(s) + N2(g) Mg3N2(s)

             Mg does not react with water to any significant extent but it does combine with steam in certain conditions

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

             Magnesium is very reactive with the halogens such as chlorine, Cl2 or bromine, Br2, and burns to form the dihalides magnesium(II) chloride, MgCl2, and magnesium(II) bromide, MgBr2, respectively.

            Mg(s) + Cl2(g) MgCl2(s)

            Mg(s) + Br2(g) MgBr2(s)



A Few Isotopes
Taken from Web Elements

Isotope Atomic mass (ma/u) Natural abundance (atom %) Nuclear spin (I) Magnetic moment (m/mN)
24Mg 23.9850423 (8) 78.99 (4) 0 0
25Mg 24.9858374 (8) 10.00 (1) 5/2 -0.85546
26Mg 25.9825937 (8) 11.01 (3) 0 0


Magnesium's radioisotopes have very short half lives; spanning from 1.3sec to 21 hours.

     Ex:   27Mg has a half life of 9.45 min

Sources of Magnesium

Magnesium is never found as a free element in nature but it is the eighth most abundant element on earth.

Magnesium can be found in minerals such as Magnesite and Dolomite (common parts of Granite) but it is most abundant in sea water.  Magnesium salts can also be found in the earth where deposits of sea salts can be found in large quantities, including South Africa and Mt. Vesuvius, Italy.


Uses of Magnesium

  • used in flares and pyrotechnics, including incendiary bombs. It was used in flash photography,
  • it is lighter than aluminum, and is used in alloys used for aircraft, car engine casings, and missile construction
  • it is used a reducing agent for the production of uranium and other metals from their salts
  • the hydroxide (milk of magnesia), chloride, sulphate (Epsom salts), and the citrate are used in medicine
  • magnesium oxide is refractory and used as bricks and liners in furnaces
  • used in computers for radio-frequency shielding


Magnesium in Biology

Magnesium has several uses in Biology.  50 % of our Magnesium is in our bones while 50% is in intercellular fluid.  While providing structure for bones Mg also has other uses.  Most of these arise from deficiency however a Mg excess can result in kidney failure and diarrhea.

Signs of excess magnesium can be similar to magnesium deficiency and include mental status changes, nausea, diarrhea, appetite loss, muscle weakness, difficulty breathing, extremely low blood pressure, and irregular heartbeat

Excess= kidney failure / squirts

Deficiency= nausea / muscle weakness

History of Magnesium

In 1618 a farmer at Epsom in England attempted to give his cows water from a well. This they refused to drink because of the water's bitter taste. However the farmer noticed that the water seemed to heal scratches and rashes. The fame of Epsom salts spread. Eventually they were recognized to be magnesium sulphate, MgSO4. Black recognized magnesium as an element in 1755. It was isolated by Davy in 1808 who electrolyzed a mixture of magnesia (magnesium oxide, MgO) and mercuric oxide (HgO). Davy's first suggestion for a name was magnium but the name magnesium is now used.


Discovered by: Joseph Black (1755)
Isolated By: Sir Humphrey Davey (1808)
Discovered in: England
Discovered When: 1755


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