JEE Main & Advanced Chemistry Metallurgy Occurrence of Metals

Occurrence of Metals

Category : JEE Main & Advanced

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

 

 

Metal Name of the ore Composition
Pb Galena PbS
Zn Zinc blende ZnS
Hg Cinnabar HgS
Ag Argentite or silver glance Pyrargyrite or ruby silver \[A{{g}_{2}}S3A{{g}_{2}}S.S{{b}_{2}}{{S}_{3}}\]
Fe Iron pyrites \[Fe{{S}_{2}}\]
Ni Kupfer nickel NiAs
Cu Copper pyrites Chalcocite or Copper glance \[CuFe{{S}_{2}}C{{u}_{2}}S\]

 

(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 \[F{{e}_{2}}{{O}_{3}}\]
Magnetite \[F{{e}_{3}}{{O}_{4}}\]
Limonite \[F{{e}_{2}}{{O}_{3}}.3{{H}_{2}}O\]
Bauxite \[A{{l}_{2}}{{O}_{3}}.2{{H}_{2}}O\]
Corundum \[A{{l}_{2}}{{O}_{3}}\]
Diaspore \[A{{l}_{2}}{{O}_{3}}.{{H}_{2}}O\]
Chromite \[FeO.C{{r}_{2}}{{O}_{3}}\]
Chromeochre \[C{{r}_{2}}{{O}_{3}}\]
Tinstone (Cassiterite) \[Sn{{O}_{2}}\]
Chrysoberyl \[BeO.A{{l}_{2}}{{O}_{3}}\]
Cuprite (Ruby copper) \[C{{u}_{2}}O\]
Pyrolusite \[Mn{{O}_{2}}\]
Zincite \[ZnO\]
Rutile \[Ti{{O}_{2}}\]
Ilmenite \[FeO.Ti{{O}_{2}}\]

 

 

Carbonates

Magnesite \[MgC{{O}_{3}}\]
Lime stone \[CaC{{O}_{3}}\]
Dolomite \[CaC{{O}_{3}}.MgC{{O}_{3}}\]
Calamine \[ZnC{{O}_{3}}\]
Malachite \[CuC{{O}_{3}}.Cu{{\left( OH \right)}_{2}}\]
Azurite \[Cu{{\left( OH \right)}_{2}}.2CuC{{O}_{3}}\]
Cerussite \[PbC{{O}_{3}}\]
Siderite \[FeC{{O}_{3}}\]

 

 

  Nitrates

Chile saltpetre \[NaN{{O}_{3}}\]
Salt petre \[KN{{O}_{3}}\]

 

 

  Sulphates

Epsom salt \[MgS{{O}_{4}}.7{{H}_{2}}O\]
Barytes \[BaS{{O}_{4}}\]
Gypsum \[CaS{{O}_{4}}.2{{H}_{2}}O\]
Glauber's salt \[N{{a}_{2}}S{{O}_{4}}.10{{H}_{2}}O\]
Anglesite \[PbS{{O}_{4}}\]
Kainite \[KCl.MgS{{O}_{4}}.3{{H}_{2}}O\]
Schonite \[{{K}_{2}}S{{O}_{4}}.MgS{{O}_{4}}.6{{H}_{2}}O\]
Polyhalite \[{{K}_{2}}S{{O}_{4}}.MgS{{O}_{4}}.CaS{{O}_{4}}.2{{H}_{2}}O\]

 

 

Phosphates and Silicates

Lepidolite (an ore of lithium) \[{{(Li,\text{ }Na,\text{ }K)}_{2}}A{{l}_{2}}{{(Si{{O}_{3}})}_{3}}{{(F,OH)}_{2}}\]
Petalite (an ore of lithium) \[LiAl{{(S{{i}_{2}}{{O}_{5}})}_{2}}\]
Triphylite (an ore of lithium) \[{{(Li,\text{ }Na)}_{3}}P{{O}_{4}},\text{ (}Fe,\text{ }Mn{{)}_{3}}\,{{(P{{O}_{4}})}_{2}}\]
Beryl (an ore of berylium) \[3BeO.A{{l}_{2}}{{O}_{3}}.6Si{{O}_{2}}\]
Willemite \[Z{{n}_{2}}Si{{O}_{4}}\]
China clay \[A{{l}_{2}}{{O}_{3}}.2Si{{O}_{2}}.2{{H}_{2}}O\]
Chlor-apatite \[3C{{a}_{3}}\,{{(P{{O}_{4}})}_{2}}.CaC{{l}_{2}}\]
Mica \[{{K}_{2}}O.3A{{l}_{2}}{{O}_{3}}.6Si{{O}_{2}}.2{{H}_{2}}O\]
Fluor-apatite \[3C{{a}_{3}}\,{{(P{{O}_{4}})}_{2}}.Ca{{F}_{2}}\]
Felspar \[KAlS{{i}_{3}}{{O}_{8}}\]
Talc \[M{{g}_{2}}\,(S{{i}_{2}}{{O}_{5}}).Mg\,{{(OH)}_{2}}\]
Asbestos \[CaM{{g}_{3}}.\,{{(Si{{O}_{3}})}_{4}}\]

 

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

 

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