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

Atomic number Element Symbol Electron configuration
4 Beryllium Be [He] 2s2
12 Magnesium Mg [Ne] 3s2
20 Calcium Ca [Ar] 4s2
38 Strontium Sr [Kr] 5s2
56 Barium Ba [Xe] 6s2
88 Radium Ra [Rn] 7s2

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 chalk.
  • 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 alkali metals.

  • 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.

alkali earth metal reactions with water

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 Chemical formula Colour
Beryllium nitride Be3N2 yellow or white powder
Magnesium nitride Mg3N2 yellow
Calcium nitride Ca3N2 red-brown

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.

With hydrogen

When alkaline earth metals are heated to high temperature with hydrogen gas, metal hydrides are given. But beryllium and magnesium react very hardly with hydrogen.

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.