Magnesium is an element of S-block. Its atomic number is 12, and the mass number is 24.305u. It has an atomic radius of 160pm. It belongs to the 2nd group in the periodic table and is located in the 3rd period.
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. Magnesium is represented as a symbol ‘Mg.’
Magnesium has a shiny grey color. It has a hexagonal close-packed crystal structure. Magnesium is paramagnetic in nature (attracts magnetic field lines). Magnesium is a metal of very low density.
Based on their electropositive properties, all the alkaline earth metals have low ionization enthalpies. Though they have filled outermost s orbital, they lose 2 electrons easily to get 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 in nature. When 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 conductivities.
As magnesium is highly reactive, it is usually not found in the free state in nature. Hence, it is extracted from two popular magnesium ores like the 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.
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 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 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.
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.
All alkaline earth metals, including magnesium, react with halogen ( 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)
Magnesium is, an electron donor as it is an electropositive element. It loses two electrons easily to achieve the nearest noble gas configuration. Magnesium is very reactive towards 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.
Magnesium does not react with bases.
As Reducing agent
All the Alkaline earth metals are electropositive in nature. Due to this they can donate electrons (to achieve stable noble gas configuration) acting as a good 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.
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 is present as a central element in the chlorophyll of green leaves in plants. 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 the molten iron.
- Magnesium is popularly used in organic chemistry to make Grignard reagent which in turn 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 aircraft in the production of flares and fireworks due to the dazzling brilliance it gives off when burnt in air.
- Magnesium is a popular component in incendiary bombs and signals.
- Magnesium carbonate is an ingredient used in the production of toothpaste.