JEE Main & Advanced Chemistry Organic Chemistry: Some Basic Principles & Techniques / कार्बनिक रसायन : कुछ मूलभूत सिद्धांत एवं तकन Occurrence of Metals

Element which have low chemical reactivity generally occur native or free or metallic state. e.g. \[Au,\,Pt,\,\]noble gas etc. Element which are chemically reactive, generally occur in the combined state. e.g. halogens, chalcogens etc. The natural materials in which the metals occur in the earth are called minerals. The mineral from which the metal is conveniently and economically extracted is called an ore. All the ores are minerals but all  minerals cannot be ores. Ores may be divided into four groups,            

(1) Metallic core (siderophile) of the earth crust contains (Mn, Fe, Co, Ni, Cu, Ru, Rb, Pd, Ag, Re, Os, Ir, Pt, Au). Entire composition of metals in earth crust may be given as,            

Al (8.3%); Ca(3.6%); Na (2.8%); K (2.6%); Mg (2.1%); Ti (0.4%); Mn (0.1%); Fe (5.1%) other metals (0.1%).            

(i) Native ores : These ores contain metals in free state, e.g., silver, gold, platinum, mercury, copper, etc. These are found usually associated with rock or alluvial materials like clay, sand, etc. sometimes lumps of pure metals are also found. These are termed nuggets. Iron is found in free state as meteroites which also have 20 to 30% nickel.            

(ii) Sulphurised and arsenical ores : These ores consist of sulphides and arsenides in simple and complex forms of metals. Important ores of this group are

(iii) Oxidised ores : In these ores, metals are present as their oxides or oxysalts such as carbonates, nitrates, sulphates, phosphates, silicates, etc.

Important ores of this group are listed below,            

Oxides

Haematite	Fe2O3
Magnetite	Fe3O4
Limonite	Fe2O3.3H2O
Bauxite	Al2O3.2H2O
Corundum	Al2O3
Diaspore	Al2O3.H2O
Chromite	FeO.Cr2O3
Chromeochre	Cr2O3
Tinstone (Cassiterite)	SnO2
Chrysoberyl	BeO.Al2O3
Cuprite (Ruby copper)	Cu2O
Pyrolusite	MnO2
Zincite	ZnO
Rutile	TiO2
Ilmenite	FeO.TiO2

Carbonates

Magnesite	MgCO3
Lime stone	CaCO3
Dolomite	CaCO3.MgCO3
Calamine	ZnCO3
Malachite	CuCO3.Cu(OH)2
Azurite	Cu(OH)2.2CuCO3
Cerussite	PbCO3
Siderite	FeCO3

Nitrates 

 Sulphates

Epsom salt	MgSO4.7H2O
Barytes	BaSO4
Gypsum	CaSO4.2H2O
Glauber?s salt	Na2SO4.10H2O
Anglesite	PbSO4
Kainite	KCl.MgSO4.3H2O
Schonite	K2SO4.MgSO4.6H2O
Polyhalite	K2SO4.MgSO4.CaSO4.2H2O

Phosphates and Silicates

Lepidolite (an ore of lithium)	(Li, Na, K)2 Al2(SiO3)3 (F,OH)2
Petalite (an ore of lithium)	LiAl(Si2O5)2
Triphylite (an ore of lithium)	(Li, Na)3PO4, (Fe, Mn)3 (PO4)2
Beryl (an ore of berylium)	3BeO. Al2O3.6SiO2
Willemite	Zn2SiO4
China clay	Al2O3.2SiO2.2H2O
Chlor-apatite	3Ca3(PO4)2.CaCl2
Mica	K2O.3Al2O3.6SiO2.2H2O
Fluor-apatite	3Ca3(PO4)2.CaF2
Felspar	KAlSi3O8
Talc	Mg2(Si2O5).Mg(OH)2
Asbestos	CaMg3.(SiO3)4

(iv) Halide ores : Metallic halides are very few in nautre. Chlorides are most common. For example.            

Common salt \[NaCl\];            

Horn silver \[AgCl\]            

Carnallite \[KCl.\,MgC{{l}_{2}}.6{{H}_{2}}O\]            

The important fluoride ores are        

Fluorspar \[Ca{{F}_{2}}\];        

Cryolite \[N{{a}_{3}}Al{{F}_{6}}\]