Magnesium is an S-block element belonging to the 2nd group in the periodic table and is located in the 3rd period.
It has an atomic number of 12 and a mass number of 24.305u.
It has an atomic radius of 160pm.
Due to this location in the periodic table, it is classified as an alkaline earth metal.
The arrangement of electrons in the Magnesium is as 1s2 2s2 2p6 3s2. It has 2 electrons in the outermost shell.
It has a completely filled outer ‘S’ orbital and it is represented by the symbol ‘Mg.’
Magnesium has shiny grey color with a crystalline structure.
It has paramagnetic properties (attracts magnetic field lines) and is a very low-density metal.
Based on their electropositive properties, all the alkaline earth metals have low ionization enthalpies.
Though they have filled the outermost s orbital, they lose 2 electrons easily to get a stable electronic configuration similar to the nearest noble gas.
Thus they are highly reactive and lose 2 electrons, thus getting oxidized. Magnesium has low first and second ionization enthalpy.
Thus Magnesium is a highly reactive metal, and even after being an abundant element, it is not found in the free state of nature.
When the magnesium strip is burnt in the air, it gives off an intense white light. Magnesium can be found in seawater.
The electrons in Magnesium are too strongly bound to get excited by flame, so it does not impart any color to the flame.
Magnesium has high electrical and thermal conductivity.
Extraction of Magnesium
Magnesium is highly reactive and is usually not found in the free state of nature.
Hence, it is extracted from two popular magnesium ores like magnesite (MgCO3) and dolomite (MgCO3.CaCO3).
Magnesium can be extracted using either of the two methods like the
- Thermal reduction of magnesium and
- Electrolysis of magnesium chloride.
Thermal reduction
Dolomite ore is crushed and heated to produce magnesium and calcium oxides. This process is called calcination.
MgCO3.CaCO3 -> MgO. CaO + 2CO2
These oxides are then mixed with crushed ferrosilicon and put into the reactor. Alumina is added to reduce the melting point of the reaction mixture. Magnesium is thus produced in vapor form in this reactor which is then condensed.
2MgO + Si -> 2Mg + 2SiO2
Electrolysis of magnesium chloride
This process is used to extract Magnesium from seawater or magnesite. Magnesite is first heated to release CO2 and give MgO.
Then, the oxide is mixed with carbon and heated in a stream of chlorine at a high temperature in an electric furnace to convert it into magnesium chloride. This
magnesium chloride is then fed into electrolytic cells. On electrolysis, Magnesium is produced at the cathode, and chlorine gas is produced at the anode.
Magnesium Properties and Characteristics
Magnesium has a completely filled outer ‘s’ orbital.
Thus it can exhibit an oxidation state of +2. It is highly reactive due to its low ionization enthalpy. Magnesium forms predominantly ionic compounds.
Reaction in air
Magnesium burns in the air giving off a dazzling white light undergoing the following reactions.
2Mg + O2 -> 2MgO
3Mg + N2 -> Mg3N2
When Magnesium reacts with oxygen or water, a very thin layer of magnesium oxide is formed on the surface.
This acts as a protective film and prevents the layers beneath it from reacting with oxygen.
With halogens
Like all other alkaline earth metals, Magnesium, reacts with halogens ( F, Cl, Br, I) at high temperatures, thus producing metallic halides.
Mg + X2 —> MgX2 where X=F, Cl, Br, I
Reaction with water
Magnesium does not react with water at cold or room temperature as it is not reactive enough (unlike sodium, potassium, etc.).
Magnesium metal does react with steam to give magnesium oxide (MgO) or magnesium hydroxide, Mg(OH)2, with excess steam and hydrogen gas (H2).
Mg(s) + 2H2O(g) → Mg(OH)2(aq) + H2(g)
With acids
Magnesium is an electron donor as it is an electropositive element. It loses two electrons quickly to achieve the nearest noble gas configuration. Magnesium is very reactive to halogens. Thus Magnesium reacts with acids liberating hydrogen gas.
Mg + 2HCl → MgCl2 + H2
Magnesium also dissolves readily in dilute acids like H2SO4 releasing Hydrogen. Thus it shows alkaline behavior.
With bases
Magnesium does not react with bases.
As Reducing agent
All Alkaline earth metals are electropositive in nature. Due to this, they can donate electrons (to achieve a stable noble gas configuration), acting as an excellent reducing agent. Magnesium has low ionization enthalpy. So it loses electrons easily, and itself gets oxidized. It thus acts as a reducing agent by donating electrons. It is a strong reducing agent.
With Hydrogen
Magnesium reacts with hydrogen upon heating to form magnesium hydride.
Mg + H2→ MgH2
In liquid ammonia
Magnesium like other alkaline earth metals dissolves in liquid ammonia. It forms a solution of ammoniated ions which are deep blue-black in color.
Magnesium Uses
- In plants, magnesium is a central element in the chlorophyll of green leaves. It is essential to capture energy from the sun which is used for carrying out photosynthesis.
- Magnesium forms alloys with other metals like aluminum, zinc, tin, etc.
- Magnesium-aluminum alloys are very lightweight and are used to manufacture components of aircraft.
- Magnesium is less dense and is used to make car seats, cameras, laptops, etc.
- Magnesium is used in metallurgical extraction procedures. It is used to remove sulfur impurities from molten iron.
- Magnesium is popularly used in organic chemistry to make Grignard reagent, which is used to make many organic chemicals.
- Milk of magnesia is a suspension of magnesium hydroxide in water. It is alkaline and is used as an antacid in medicine. It is used to neutralize the secretion of excess hydrochloric acid in the stomach.
- Magnesium is used in laxatives to clear the bowels for surgical procedures and to cure constipation.
- Magnesium is used in the production of flares and fireworks due to the dazzling brilliance it gives off when burnt in the air.
- Magnesium is a popular component in incendiary bombs and signals.
- Magnesium carbonate is an ingredient used in the production of toothpaste.