Alkaline Earth Metals Reactions, Uses, Properties
The general electron configuration of alkaline metals is [noble gas] ns2 where n represents
the valence shell. These metals forms +2 ions only. Alkaline earth metals are less reactive than alkali metals.
Elements of Alkaline earth metals with electron configuration
Occurrence of Alkaline earth metals
Occurrence of Magnesium (Mg)
Occurrence of Calcium (Ca)
- In vast sedimentary rocks of CaCO3 existing as awhole mountain ranges of limestone, marble and
- As Gypsum ( CaSO4.2H2O )
- As fluorite (CaF2)
- As fluoroapatite ( 3Ca3(PO4)2.CaF2 )
Chemical properties of Alkaline earth metals
Reactions of water and alkaline earth metals
Alkaline earth metals react in lesser tendency with water when it compares with
- Beryllium and Magnesium do not react with cold water.
- Magnesium reacts with steam and form magnesium oxide. But beryllium does not react with steam.
- Calcium, strontium and barium react with water and form hydroxides and hydrogen gas. Strontium hydroxide and
barium hydroxide are strong bases.
Hydroxides of alkaline earth metals' are basic. Also basic strength increases down the family.
Ex: Sr(OH)2 is more basic than Ca(OH)2.
Reactions between air and alkaline earth metals
Air contains oxygen and nitrogen gases. Alkaline earth metals reacts with oxygen and nitrogen gases
in different ways.
- Due to formation of film of oxides of beryllium and magnesium, they do not continuously react with oxygen.
But powdered beryllium burns and gives beryllium oxide (BeO) and beryllium nitride (Be3N2).
- When magnesium burns in air and give a mixture of magnesium oxide (MgO) and magnesium nitride (Mg3N2).
- Calcium, strontium and barium easily react with air give oxides and nitrides.
- Strontium and barium can make peroxides with oxygen gas.
Colours of alkaline earth metal nitrides
|Alkaline metal nitride
||yellow or white powder
Alkaline earth metal nitrides and oxygen reaction
Alkaline earth metal nitrides reacts with oxygen and release nitrogen gas and form alkaline earth metal oxides.
Alkaline earth metal nitrides and hydrogen gas reaction
Alkaline earth metal nitrides reacts with hydrogen gas and release
ammonia gas and form alkaline earth metal hydride.
When alkaline earth metals are heated to high temperature with hydrogen gas, metal hydrides are given. But beryllium and magnesium react very hardly
Here, hydrogen is reduced to hydride ion and alkaline earth metal is oxidized.
These metal hydrides can emit hydrogen gas when they react with compounds which can supply H+ ions. As an example, when calcium
hydride is added to water, calcium hydroxide and hydrogen gas are given as products.
Halogen and alkaline earth metals
Alkaline earth metals react with halogens and form halides. This reaction is a exothermic reaction.
Ca + Cl2 → CaCl2
Ba + I2 → BaI2
Ammonia and alkaline earth metals
3Mg + 2NH3 → Mg3N2 + H2
Due to release of hydrogen gas, ammonia behaves as an acid.
Sulfur and alkaline earth metals reactions
Mg + H2S → MgS
This metal sulfide reacts with dilute acids and emit hydrogen sulfide gas.
MgS + HCl → MgCl2 + H2S
Phosphorous and alkaline earth metal reactions
Alkaline earth metal phosphide are given when heat is supplied.
3Ca + 2P → Ca3P2
Uses of alkaline earth metals
Now we are going to discuss uses of each element in 2nd group.
Uses of beryllium
- For manufacturing of many alloys. As an example, copper beryllium alloys are used in the preparation of high strength springs.
- Metallic beryllium is used for making windows of X-ray tubes.
Uses of magnesium
- Mg is the lightest constructional metal in industry having a density less than two thirds of Al.
- For manufacturing alloying metals.
- For cathodic protection of other metals as oxygen scavenger.
- The compounds of magnesium such as Mg(OH)2 and MgCO3 are used in making tooth pastes.
- Mg is used as a dioxidizer for removing last traces of oxygen from Cu, steel,etc.
Uses of plaster of paris
- for producing moulds for pottery, ceramics, etc
- used for making statues, models and other decorative materials.
- It is used in the building industry as well as plasters.
- In dentistry
- Plaster of paris is used in surgical bandages known as plasters for setting broken and fractured bones in the
body because it immoblises the affected part of the organ where there is a bone fracture or sprain.