GROUP II METALS — AT A GLANCE

Also called: Alkaline Earth Metals

 Members:
Beryllium (Be) →Magnesium (Mg) → Calcium (Ca) → Strontium (Sr) → Barium (Ba) → Random (Ra)

Why are they called Group II metals?

They have two electrons in their outermost shell and commonly lose these electrons to form M²⁺ ions.

Example:

Ca → Ca²⁺ + 2e⁻

General Properties

i. Have 2 valence electrons

ii. Form M²⁺ ions

iii. Good conductors of heat and electricity

iv. Generally form ionic compounds

v. Reactivity generally increases down the group

vi. Their oxides and hydroxides are generally basic

vii. React with acids to produce salt + hydrogen

viii. Some react with water to produce metal hydroxide + hydrogen

CALCIUM — Ca

Quick identity

Symbol: Ca
Atomic number: 20
Group: II
Common ion: Ca²⁺

Electronic configuration: 1s22s22p63s23p64s2

Calcium is a reactive metal, so you will not normally find it as free calcium in nature. Instead, it occurs combined with other elements.

OCCURRENCE

Important calcium minerals (Ores) include:

Mineral	Formula
Limestone	CaCO₃
Chalk	CaCO₃
Marble	CaCO₃
Gypsum	CaSO₄·2H₂O
Fluorite	CaF₂
Dolomite	CaMg(CO₃)₂

NOTE 

 Limestone, chalk and marble are mainly forms of calcium carbonate, CaCO₃.

 EXTRACTION OF CALCIUM

Calcium is too reactive to be extracted by heating its compounds with carbon.

It is extracted by electrolysis of molten calcium chloride. CaF2 is added to lower its melting point

Diagram: Electrolytic cell of extraction of Calcium 

Electrolyte-:  Molten CaCl₂

At the cathode

Calcium ions gain electrons:

Ca²⁺ + 2e⁻ → Ca

At the anode-: Chloride ions lose electrons:

2Cl⁻ → Cl₂ + 2e⁻

Overall reaction

CaCl₂(l) → Ca(s) + Cl₂(g)

 Note

Calcium is extracted by electrolysis, not by carbon reduction.

Physical properties

Calcium is:

1.  Silvery-white

2. Relatively soft

3. A good conductor of heat and electricity

4. Less dense than many common metals

Chemical properties

1. Reaction with water

Ca + 2H₂O → Ca(OH)₂ + H₂

2. Reaction with oxygen: calcium tarnished in air when exposed to atmospheric gasses

2Ca + O₂ → 2CaO

3. Reaction with hydrochloric acid

Ca + 2HCl → CaCl₂ + H₂

4. Reaction with chlorine

Ca + Cl₂ → CaCl₂

USES OF CALCIUM 

Calcium compounds are more commonly used than calcium metal.

They are used in:

1. Manufacture of cement

2. Production of lime

3. Treatment of acidic soils

4. Manufacture of plaster

5. Building materials

6. Various industrial processes

Calcium is also an essential mineral for bones and teeth.

           Compounds of Calcium

Calcium compound	Formula	Method of preparation	Uses
Calcium oxide (quicklime)	CaO	By heating limestone strongly: CaCO₃ → CaO + CO₂	Manufacture of cement; neutralising acidic soils; production of calcium hydroxide; extraction of some metals
Calcium hydroxide (slaked lime)	Ca(OH)₂	By adding water to calcium oxide: CaO + H₂O → Ca(OH)₂	Making mortar and plaster; neutralising acidic soils; manufacture of bleaching powder; testing for CO₂
Calcium carbonate	CaCO₃	Precipitation by passing CO₂ into limewater or by reacting calcium hydroxide with a soluble carbonate	Manufacture of cement and lime; production of glass; used as a building material; manufacture of chalk
Calcium chloride	CaCl₂	By reacting calcium carbonate with hydrochloric acid: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂	Drying agent; removal of ice from roads; dust control; used in laboratories and industry
Calcium sulphate	CaSO₄	Neutralization reaction.reacting calcium carbonate with dilute sulphuric acid:	Manufacture of plaster of Paris; making casts; construction materials
Calcium sulphate hemihydrate (Plaster of Paris)	CaSO₄·½H₂O	By heating gypsum, CaSO₄·2H₂O, at about 120°C:	Medical casts; moulds; decorative work; making models
Calcium sulphate dihydrate (Gypsum)	CaSO₄·2H₂O	Obtained naturally as the mineral gypsum;	Manufacture of plaster of Paris; cement manufacture; production of wallboard
Calcium carbide	CaC₂	By heating calcium oxide with carbon in an electric furnace: CaO + 3C → CaC₂ + CO	Production of ethyne (acetylene); metal cutting and welding; production of some chemicals
Calcium nitrate	Ca(NO₃)₂	Neutralization reacting calcium carbonate with nitric acid:	Nitrogen fertiliser; manufacture of explosives and other chemicals
Calcium phosphate	Ca₃(PO₄)₂	Prepared by reacting a soluble calcium salt with a soluble phosphate, producing a precipitate	Manufacture of fertilisers; production of phosphoric compounds; important component of bones and teeth