Transition elementsTransition elements

[d- block elements][d- block elements]

Position in the periodic tablePosition in the periodic table

20_431

Ce

Th

Pr

Pa

Nd

U

Pm Sm

Pu

Eu

Am

Gd

Cm

Tb

Bk

Dy

Cf

Ho

Es

Er

Fm

Tm

Md

Yb

No

Lu

Lr

Sc

Y

La

Ac

Ti

Zr

Hf

Unq

V

Nb

Ta

Unp

Cr

Mo

W

Unh

Mn

Tc

Re

Uns

Fe

Ru

Os

Co

Rh

Ir

Ni

Pd

Pt

Cu

Ag

Au

Zn

Cd

Hg

Uno Une Uun Uuu

Np

Where are the transition Where are the transition metals?metals?

The transition metals are the block of elements located between group 2 and group 13 of the periodic table.

Ac Rf Db Sg Bh Hs Mt Ds Rg

La Hf Ta W Re Os Ir Pt Au Hg

Y Zr Nb Mo Tc Ru Rh Pd Ag Cd

Sc Ti V Cr Mn Fe Co Ni Cu Zn

?

Here, the word ‘transition’ is used to mean ‘in-between’.

group 2 group 13

The transition metals are known as ‘typical’ metals because of their physical properties. They are:

Why transition metals are called typical Why transition metals are called typical metals?metals?

lustrous (bright and shiny).

high density.

good conductors of heat and electricity.

high melting and boiling points (except mercury, which is liquid at room temperature).

hard and strong.

malleable (can be bent and pressed into different shapes) and ductile (can be drawn into wires).

All 'd' block elements are classified into four transition series namely:

• 3d series in the 4th period – 10 elements

• 4d series in the 5th period- 10 elements

• 5d series in the 6th period- 10 elements

• 6d series in the 7th period having incomplete elements.

► All the elements belonging to I B, II B, III B, IV B, V B, VI B, All the elements belonging to I B, II B, III B, IV B, V B, VI B, VII B, VIII B (i.e.3 TO 12) are called transition elements. VII B, VIII B (i.e.3 TO 12) are called transition elements.

► They resemble each other in several physical and chemical They resemble each other in several physical and chemical properties. properties.

► They are all metals. They are all metals. ► They are called transition elements because they are They are called transition elements because they are

placed between the most reactive metals on the left and placed between the most reactive metals on the left and non-metals on the right. non-metals on the right.

► Their compounds are colored. Their compounds are colored. ► They exhibit variable valency.They exhibit variable valency.► They form co-ordination compounds.They form co-ordination compounds.► Tend to be hard and durable.Tend to be hard and durable.► Have high tensile strength.Have high tensile strength.► Have good mechanical properties.Have good mechanical properties.

GENERAL PROPERTIES OF TRANSITION ELEMENTS

Electronic ConfigurationElectronic Configuration

General outer electronic configuration isGeneral outer electronic configuration is (n - 1) d(n - 1) d1-101-10 ns ns1-21-2..

Each “additional” electron enters the (n-1) sub-shell.Each “additional” electron enters the (n-1) sub-shell.

'd' block elements are those in which the added 'd' block elements are those in which the added electron goes into one of the 'd' orbitals.electron goes into one of the 'd' orbitals.

These elements have valence electrons in both their These elements have valence electrons in both their

outermost and penultimate shells (second outermost)outermost and penultimate shells (second outermost)

1s

2s

3s

4s

2p

3p

3d

Energy

Sc -1s2 2s2 2p6 3s2 3p6 3d1 4s2

4p

Electronic ArrangementElectronic ArrangementElEl ZZ 3d3d 4s4s

ScSc 2121 [Ar][Ar]

TiTi 2222 [Ar][Ar]

VV 2323 [Ar][Ar]

CrCr 2424 [Ar][Ar]

MnMn 2525 [Ar][Ar]

FeFe 2626 [Ar][Ar]

CoCo 2727 [Ar][Ar]

NiNi 2828 [Ar][Ar]

CuCu 2929 [Ar][Ar]

ZnZn 3030 [Ar][Ar]

Chromium and CopperChromium and Copper

Cr and Cu don’t fit the pattern of Cr and Cu don’t fit the pattern of building up the 3d sub-shell, why?building up the 3d sub-shell, why?

1s

2s

3s

4s

2p

3p

3d

Energy

Cr-1s2 2s2 2p6 3s2 3p6 3d5

4s1

4p

CHROMIUM

1s

2s

3s

4s

2p

3p

3d

Energy

Cu-1s2 2s2 2p6 3s2 3p6 3d10

4s1

4p

GENERAL CHARACTERISTICS OFGENERAL CHARACTERISTICS OF

TRANSITION ELEMENTS TRANSITION ELEMENTS

The members belonging to a given transition The members belonging to a given transition series do not differ so much from one another as series do not differ so much from one another as those of representative elements of the same those of representative elements of the same period.period.

It is due to as there is no change in the number of It is due to as there is no change in the number of ns electrons and only change occurs in thens electrons and only change occurs in the

(n- 1)d electrons from member to member in a (n- 1)d electrons from member to member in a period. period.

ScSc3+ 3+ andand ZnZn2+ 2+ are not the typical TM ionsare not the typical TM ions

Not all d block elements have incompleteNot all d block elements have incomplete

d sub-shells.d sub-shells.

e.g. Zn has e.c. of [Ar]3de.g. Zn has e.c. of [Ar]3d10104s4s22, the Zn, the Zn2+2+ ion ([Ar] ion ([Ar]

3d3d1010) is not a typical TM ion) is not a typical TM ion

Similarly Sc forms ScSimilarly Sc forms Sc3+3+ which has the stable e.c which has the stable e.c of Ar. Scof Ar. Sc3+3+ has no 3d electrons has no 3d electrons

What is a transition metal?What is a transition metal?

► For this reason, For this reason, a transition metal isa transition metal is

defined as being an element whichdefined as being an element which

forms at least one ion with a partiallyforms at least one ion with a partially

filled sub-shell of d electrons.filled sub-shell of d electrons. In period 4 only Ti-Cu are TM’s!In period 4 only Ti-Cu are TM’s! Note that when d block elements form ions the s Note that when d block elements form ions the s

electrons are lostelectrons are lost first first

1. Metallic character1. Metallic character► Most of the transition elements of the first row form Most of the transition elements of the first row form

metallic bonds due to the presence of incomplete metallic bonds due to the presence of incomplete outermost energy level. So, all the transition outermost energy level. So, all the transition elements exhibit metallic characters. elements exhibit metallic characters.

► The strength of the metallic bond depends upon The strength of the metallic bond depends upon the number of unpaired d-electrons. As the number the number of unpaired d-electrons. As the number increases the strength also increases. Due to the increases the strength also increases. Due to the absence of unpaired electrons 'Zn' is not a hard absence of unpaired electrons 'Zn' is not a hard metal.metal.

Hg exists as a liquid at room Hg exists as a liquid at room temperaturetemperature

Mercury has completely filled dMercury has completely filled d1010 electronic configuration. Hence the electronic configuration. Hence the extent of metallic bond formation is extent of metallic bond formation is less as the orbitals are completely less as the orbitals are completely filled. due to weak interatomic forces filled. due to weak interatomic forces of attraction, Hg exists as a liquid at of attraction, Hg exists as a liquid at room temperatureroom temperature

(Downward trend in melting points from Zn (420°C) (Downward trend in melting points from Zn (420°C) through Cd (321 ° C) to Hg (-39 ° C)through Cd (321 ° C) to Hg (-39 ° C)

2. Atomic and Ionic radii2. Atomic and Ionic radii

► Atomic radii:Atomic radii:► In the transition elements the atomic radii In the transition elements the atomic radii

decreases with increase in atomic number. decreases with increase in atomic number.

► At the end of series it slightly increase due At the end of series it slightly increase due to increase in electron-electron repulsion.to increase in electron-electron repulsion.

► The atomic radii of 4-d and 5-d series are The atomic radii of 4-d and 5-d series are very close due to lanthanide contraction. very close due to lanthanide contraction.

20_435

0.2

Ato

mic

rad

ii (n

m)

Atomic number

La

Hf

TaW

Re OsIr Pt

Au

Zr

Y

NbMo

Tc Ru

Rh Pd

Ag

Sc

Ti

VCr

Mn Fe Co NiCu

1st series (3d)

2nd series (4d)

3rd series (5d)

0.1

0.15

Atomic radii :

► Ionic radii:Ionic radii:

► In the first row transition elements the ionic In the first row transition elements the ionic radii decreases with increase in atomic number. radii decreases with increase in atomic number.

► The value of ionic radii also depends on the The value of ionic radii also depends on the oxidation state of metals.oxidation state of metals.

► As the oxidation state increases the ionic radii As the oxidation state increases the ionic radii decreases (nuclear pull increase)and as the decreases (nuclear pull increase)and as the oxidation state decreases the ionic radii oxidation state decreases the ionic radii increases.increases.

3. 3. CCoolloorreedd ions ions

► In the first row transition elements all the elements In the first row transition elements all the elements except Zn form colored ions. except Zn form colored ions.

► As these elements have incomplete d-orbital, some As these elements have incomplete d-orbital, some amount of energy is required to promote the amount of energy is required to promote the electrons from lower energy level to higher energy electrons from lower energy level to higher energy level. level.

► This process exhibits radiations from which the This process exhibits radiations from which the compounds absorb a particular color. compounds absorb a particular color.

► But some elements other than Zn also appear But some elements other than Zn also appear colorless depending on their oxidation state. For colorless depending on their oxidation state. For e.g., Sce.g., Sc3+3+, Ti, Ti4+4+ and Cu and Cu++ have completely filled d- have completely filled d-orbitals and hence they appear colorless.orbitals and hence they appear colorless.

►Most of the transition elements form colored Most of the transition elements form colored compounds both in solid state as well as in compounds both in solid state as well as in aqueous solution. aqueous solution.

► It is already studied that the transition metals It is already studied that the transition metals have incomplete d-orbital. The electrons are to have incomplete d-orbital. The electrons are to be promoted from a lower energy level to a be promoted from a lower energy level to a higher energy level. Some amount of energy is higher energy level. Some amount of energy is required for this process and the radiations of required for this process and the radiations of light are observed in the visible region. The light are observed in the visible region. The compounds absorb a particular color from the compounds absorb a particular color from the radiation and the remaining ones are emitted.radiation and the remaining ones are emitted.

►For e.g., CuFor e.g., Cu2+2+ are bluish green in color due to are bluish green in color due to absorption of red light wavelength. As Zn has absorption of red light wavelength. As Zn has completely filled d-orbitals it cannot absorb completely filled d-orbitals it cannot absorb radiation and hence Znradiation and hence Zn2+2+ salts are white. salts are white.

Most transition metals form coloured compounds.

Copper (II) sulfate crystals (CuSO4.H2O) is blue – these can be turned white by heating the crystals to remove the water.

Iron (III) oxide (Fe2O3) is red/brown – when hydrated this is rust.

Iron (II) oxide (FeO2) is black.

For example:

Copper (I) oxide Cu2O is red/brown.

Copper (II) oxide CuO is

black.

Color and MagnetismColor and Magnetism

Magnetic properties are due to unpaired electrons.

Electrons in partially filled d sublevel absorbs visible light , moves to slightly higher energy d orbital.

4. Complex formation4. Complex formation

► All the first row transition elements form All the first row transition elements form complexes. These complexes contain negative ions complexes. These complexes contain negative ions or neutral molecules linked to a metal ion. These or neutral molecules linked to a metal ion. These are called as ligands. Some examples of the are called as ligands. Some examples of the complex compounds formed by first row transition complex compounds formed by first row transition elements are:elements are:

► As the transitions metals are small in size they form As the transitions metals are small in size they form large number of complexes. large number of complexes.

► [Fe(CN)6]4-, [Cu(NH3)4]2+, [Ni(CN)4]2-, [Fe(CN)6]4-, [Cu(NH3)4]2+, [Ni(CN)4]2-, [Zn(NH3)4]2+32+2+ [Zn(NH3)4]2+32+2+

The transition elements show variable oxidation states. The transition elements show variable oxidation states.

► By the study of electronic configuration of transition metals it is By the study of electronic configuration of transition metals it is understood that variable oxidation state can be formed as there understood that variable oxidation state can be formed as there are both are both ns and (n-1)d electrons in bondingns and (n-1)d electrons in bonding..

► The participation of ns electrons in bonding leads to +2 oxidation The participation of ns electrons in bonding leads to +2 oxidation state which is a lower oxidation state. state which is a lower oxidation state.

► The participation of (n-1)d electrons in bonding leads to higher The participation of (n-1)d electrons in bonding leads to higher oxidation states like +3, +4, +5, +6 etc. oxidation states like +3, +4, +5, +6 etc.

► These oxidation states depend upon the nature of combination of These oxidation states depend upon the nature of combination of transition metals with other elements. transition metals with other elements.

► The oxidation state increases with atomic number. This increase is The oxidation state increases with atomic number. This increase is related to groups. The most common oxidation state of the related to groups. The most common oxidation state of the elements of first transition series is +2. elements of first transition series is +2.

► Ionic bonds are formed in lower oxidation state transition elements Ionic bonds are formed in lower oxidation state transition elements whereas covalent bonds are formed in higher oxidation states.whereas covalent bonds are formed in higher oxidation states.

► Zn is an exception among them as it has fully filled d-orbital, it exhibits only Zn is an exception among them as it has fully filled d-orbital, it exhibits only +2 oxidation state. The oxidation states of first row transition metals are +2 oxidation state. The oxidation states of first row transition metals are shown below.shown below.

5. Variable5. Variable Oxidation StateOxidation State

Oxidation States of TM’sOxidation States of TM’s

ScSc TiTi VV CrCr MnMn FeFe CoCo NiNi CuCu ZnZn+1+1

+2+2 +2+2 +2+2 +2+2 +2+2 +2+2 +2+2 +2+2

+3+3 +3+3 +3+3 +3+3 +3+3 +3+3 +3+3 +3+3 +3+3

+4+4 +4+4 +4+4

+5+5

+6+6 +6+6 +6+6

+7+7

Oxidation States of TM’sOxidation States of TM’s

Stability of OS’sStability of OS’s

►Change from one OS to another is a Change from one OS to another is a redox reactionredox reaction

►Relative stability of different OS’s can Relative stability of different OS’s can be predicted by looking at Standard be predicted by looking at Standard Electrode Potentials Electrode Potentials EE values values

Stability of OS’sStability of OS’s►General trendsGeneral trends

Higher OS’s become less stable Higher OS’s become less stable relative to lower ones on moving from relative to lower ones on moving from left to right across the series.left to right across the series.

Compounds containing TM’s in high Compounds containing TM’s in high OS’s tend to be oxidising agents e.g OS’s tend to be oxidising agents e.g MnOMnO44

--

Compounds with TM’s in low OS’s are Compounds with TM’s in low OS’s are often reducing agents e.g Voften reducing agents e.g V2+2+ & Fe & Fe2+2+

Stability of OS’sStability of OS’s

► General trends (continued)General trends (continued) Relative stability of +2 state with respect to Relative stability of +2 state with respect to

+3 state increases across the series+3 state increases across the series For compounds early in the series, +2 state For compounds early in the series, +2 state

highly reducing highly reducing ► E.g. VE.g. V2+2+(aq) & Cr(aq) & Cr2+2+(aq) strong reducing agents(aq) strong reducing agents

Later in series +2 stable, +3 state highly Later in series +2 stable, +3 state highly oxidisingoxidising

► E.g. CoE.g. Co3+3+ is a strong oxidising agent, Ni is a strong oxidising agent, Ni3+3+ & Cu & Cu3+3+ do do not exist in aqueous solution.not exist in aqueous solution.

6. Catalytic property6. Catalytic property

► TM’s and their compounds are TM’s and their compounds are effective andeffective and

important catalysts due to,important catalysts due to,

The The availability of 3d and 4s eavailability of 3d and 4s e-- Ability to change OSAbility to change OS

f- block elementsf- block elements

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Ce

Th

Pr

Pa

Nd

U

Pm Sm

Pu

Eu

Am

Gd

Cm

Tb

Bk

Dy

Cf

Ho

Es

Er

Fm

Tm

Md

Yb

No

Lu

Lr

Sc

Y

La

Ac

Ti

Zr

Hf

Unq

V

Nb

Ta

Unp

Cr

Mo

W

Unh

Mn

Tc

Re

Uns

Fe

Ru

Os

Co

Rh

Ir

Ni

Pd

Pt

Cu

Ag

Au

Zn

Cd

Hg

Uno Une Uun Uuu

Np

►The f - block elements are also called The f - block elements are also called as inner transition elements. as inner transition elements.

►As the last electron enters the f-orbital As the last electron enters the f-orbital these elements are called as f - block these elements are called as f - block elements. elements.

►These are divided into two series: These are divided into two series:

Lanthanides and actinides. Lanthanides and actinides. ►Lanthanides are the elements in which Lanthanides are the elements in which

the last electron enters into 4f - orbital. the last electron enters into 4f - orbital. ►Actinides are the elements in which Actinides are the elements in which

the last electron enters into 5f-orbital. the last electron enters into 5f-orbital.

Oxidation statesOxidation states

►Lanthanides exhibit different Lanthanides exhibit different oxidation states like +2, +3 and +4.oxidation states like +2, +3 and +4.

► Among these +3 is the most stable Among these +3 is the most stable oxidation state. oxidation state.

►The elements that attain stable The elements that attain stable electronic configuration by losing 2 electronic configuration by losing 2 or 4 electrons exhibit +2 and +4 or 4 electrons exhibit +2 and +4 oxidation states.oxidation states.

Lanthanide contractionLanthanide contraction

► In lanthanides there is a gradual decrease in In lanthanides there is a gradual decrease in atomic size, atomic radii and ionic radii with atomic size, atomic radii and ionic radii with increase in atomic number. This regular increase in atomic number. This regular decrease is known as lanthanide contraction.decrease is known as lanthanide contraction.

► CausesCauses► In lanthanides, the nuclear charge increases by In lanthanides, the nuclear charge increases by

one unit at each successive element and this one unit at each successive element and this new electron enters the 4f-subshell. Due to the new electron enters the 4f-subshell. Due to the peculiar shapes of f-orbitals, there is imperfect peculiar shapes of f-orbitals, there is imperfect shielding of electrons from the nuclear shielding of electrons from the nuclear attraction. As a result of this the size of attraction. As a result of this the size of lanthanide atoms decreases.lanthanide atoms decreases.

METALLURGY OF IRONMETALLURGY OF IRON

►Ores of IronOres of Iron

METALLURGY OF IRONMETALLURGY OF IRON - - BLAST FURNACEBLAST FURNACE

METALLURGY OF IRONMETALLURGY OF IRON :Reactions :Reactions► Combustion ZoneCombustion Zone Reaction : Combustion of cokeReaction : Combustion of coke Temperature of the region: 2000°C Temperature of the region: 2000°C

C + OC + O2 2 CO CO22

► Fusion ZoneFusion Zone Reaction: Reduction of carbon dioxide to carbon monoxideReaction: Reduction of carbon dioxide to carbon monoxide Temperature of the region: 1300º C Temperature of the region: 1300º C

COCO2 2 + O+ O2 2 2CO2CO

► Decomposition of LimestoneDecomposition of Limestone► The lime stone (CaCO3) decomposes to give carbon dioxide The lime stone (CaCO3) decomposes to give carbon dioxide

and quicklime (CaO)and quicklime (CaO)

CaCOCaCO33 CaO + CO CaO + CO22

The above reaction is endothermic and the temperature in the The above reaction is endothermic and the temperature in the

region falls to about 800-1000ºC.region falls to about 800-1000ºC.

► Formation of SlagFormation of Slag The quicklime reacts with acidic impurities such as silica (SiOThe quicklime reacts with acidic impurities such as silica (SiO22) )

and forms a slag which melts and collects above the iron at and forms a slag which melts and collects above the iron at the bottom of the furnace. Slag is an easily fusible mass the bottom of the furnace. Slag is an easily fusible mass having a low melting point.having a low melting point.

CaO + SiOCaO + SiO22 CaSiO CaSiO33

► Reduction ZoneReduction Zone Reduction of hematite to molten iron takes place here.Reduction of hematite to molten iron takes place here.

FeFe22OO3 3 + 3CO 2Fe + CO+ 3CO 2Fe + CO22

Temperature of the region: 500-700º C Temperature of the region: 500-700º C In the upper region of the furnace, the CO reduces the In the upper region of the furnace, the CO reduces the

hematite to molten iron and oxidizes it self to COhematite to molten iron and oxidizes it self to CO22.. ► The molten iron produced is collected, poured into moulds The molten iron produced is collected, poured into moulds

and solidified to give pig iron. and solidified to give pig iron. ► Pig iron contains carbon, sulphur, phosphorus, silicon and Pig iron contains carbon, sulphur, phosphorus, silicon and

manganese as impurities manganese as impurities

METALLURGY OF COPPERMETALLURGY OF COPPER► CONCENTRATIONCONCENTRATION    

   The finely crushed ore is concentrated by Froth-Floatation The finely crushed ore is concentrated by Froth-Floatation process. The finely crushed ore is suspended in    water process. The finely crushed ore is suspended in    water containing a little amount of pine oil. A blast of air is passed containing a little amount of pine oil. A blast of air is passed through the suspension. The particles    get wetted by the oil through the suspension. The particles    get wetted by the oil and float as a froth which is skimmed. The gangue sinks to the and float as a froth which is skimmed. The gangue sinks to the bottom.bottom.

► ROASTINGROASTING       The concentrated ore is then roasted in a furnace in the The concentrated ore is then roasted in a furnace in the

presence of a current of air. Sulphur is oxidized to SOpresence of a current of air. Sulphur is oxidized to SO22 and and impurities of arsenous and antimony are removed as volatile impurities of arsenous and antimony are removed as volatile oxides.oxides.

2CuFeS2 + O2 Cu2S + 2FeS + SO2 Cuprous sulphide and ferrous sulphide are further oxidized into their oxides.2Cu2S + 3O2 2Cu2O + 2SO2 2FeS + 3O2 2FeO + 2SO2

[S + O2 SO2 4As + 3O2 As2O3

4Sb + 3O2 2Sb2O3 ]

► SMELTING SMELTING

      The roasted ore is mixed with coke and silica (sand) The roasted ore is mixed with coke and silica (sand) SiOSiO22 and is introduced in to a blast furnace. The and is introduced in to a blast furnace. The hot air is blasted and FeO is converted in to ferrous hot air is blasted and FeO is converted in to ferrous silicate (FeSiO3).silicate (FeSiO3).

FeO + SiOFeO + SiO22 FeSiO FeSiO33 Cu2O + FeS CuCu2O + FeS Cu22S + FeOS + FeO      

FeSiOFeSiO33 (slag) floats over the molten matte of (slag) floats over the molten matte of copper.copper.

► BESSEMERIZATIONBESSEMERIZATION         Copper metal is extracted from molten matte Copper metal is extracted from molten matte

through bessemerization . through bessemerization . The matte is introduced in to Bessemer converter The matte is introduced in to Bessemer converter

which uphold by tuyers. The air is blown through which uphold by tuyers. The air is blown through the molten matte. Blast of air converts Cuthe molten matte. Blast of air converts Cu22S partly S partly into Cuinto Cu22O which reacts with remaining CuO which reacts with remaining Cu22S to give S to give molten copper.molten copper.

2Cu2Cu22S + 3OS + 3O22 2Cu 2Cu22O + 2SOO + 2SO22

2Cu2Cu22O + CuO + Cu22S 6Cu + SOS 6Cu + SO22

The copper so obtained is called "Blister copper" because, as it solidifies, SO2 hidden in it escapes out producing blister on its surface.

METALLURGY OF ZINCMETALLURGY OF ZINC

►The important ores of zinc are The important ores of zinc are ►Zinc blende Zinc blende (Zns), important one(Zns), important one►Calamine (ZnCOCalamine (ZnCO33))

►Zincite (ZnO)Zincite (ZnO)

►Concentration :Concentration :by froth floatation.by froth floatation.►Roasting: (calcination if calamine)Roasting: (calcination if calamine)

2ZnS + 3O2ZnS + 3O22 2ZnO + 2SO 2ZnO + 2SO22

► Reduction:Reduction:

a) Smelting:a) Smelting:

ZnO + C Zn + CO ZnO + C Zn + CO 2CO + O2CO + O22 2CO 2CO22 ( burns with blue ( burns with blue

flame)flame)

b) Electrolytic :b) Electrolytic :

Electrolyte : Zinc sulphateElectrolyte : Zinc sulphate

ZnO + HZnO + H22SOSO4 4 ZnSOZnSO44 + + HH22OO

Cathode : Aluminium sheetsCathode : Aluminium sheets

ZnZn++++ + 2e Zn + 2e Zn (99.99 % pure)(99.99 % pure)

Anode : LeadAnode : Lead

METALLURGY OF SILVER : METALLURGY OF SILVER : Cyanide processCyanide process► The important ores of silver are: The important ores of silver are:

Argentite or silver glance (AgArgentite or silver glance (Ag22S), S), Copper silver glance (AgCopper silver glance (Ag22S CuS Cu22S)S)Horn silver ( AgCl) Horn silver ( AgCl) Ruby silver (AgRuby silver (Ag33SbSSbS33).).

► Silver is extracted from the ore-argentite (AgSilver is extracted from the ore-argentite (Ag22S). S). ► Cyanide treatment:Cyanide treatment:► The process of extraction of silver is called as cyanide The process of extraction of silver is called as cyanide

process as sodium cyanide solution is used. The ore is process as sodium cyanide solution is used. The ore is crushed, concentrated and then treated with sodium crushed, concentrated and then treated with sodium cyanide solution. This reaction forms sodium argento cyanide solution. This reaction forms sodium argento cyanide.cyanide.

AgAg22S + 2NaCN 2NaCN + NaS + 2NaCN 2NaCN + Na22SS

AgCN + 2NaCN Na[Ag(CN)AgCN + 2NaCN Na[Ag(CN)22] x2] x2

AgAg22S + 4NaCN 2Na[Ag(CN)S + 4NaCN 2Na[Ag(CN)22] + Na] + Na22SS Since the reaction is reversible,NaSince the reaction is reversible,Na22S must be removed.S must be removed.

The solution of sodium argento cyanide The solution of sodium argento cyanide combines with zinc dust and precipitated combines with zinc dust and precipitated silver.silver.

Na[Ag(CN)Na[Ag(CN)22] [NaCN + AgCN]x2] [NaCN + AgCN]x2

AgCN + Zn Zn(CN)AgCN + Zn Zn(CN)22 +2Ag +2Ag

2Na[Ag(CN)2Na[Ag(CN)22] + Zn 2NaCN +Zn(CN)] + Zn 2NaCN +Zn(CN)22 + + 2Ag2Ag

STUDY OF COMPOUNDSSTUDY OF COMPOUNDS

► SILVER NITRATESILVER NITRATE

Preparation:Preparation:

In the preparation of silver nitrate dilute nitric acid In the preparation of silver nitrate dilute nitric acid is used. Silver combines with HNOis used. Silver combines with HNO33 and forms silver and forms silver nitrate. nitrate.

3Ag + 4HNO3Ag + 4HNO 3 3 3AgNO3AgNO3 3 + 2H+ 2H22OO + NO+ NO

USE OF SILVER NITRATE IN USE OF SILVER NITRATE IN PHOTOGRAPHYPHOTOGRAPHY

► Silver nitrate is a photosensitive crystal Silver nitrate is a photosensitive crystal commonly used in early commonly used in early photographyphotography. Today . Today silver halidessilver halides are used, but silver nitrate is an are used, but silver nitrate is an intermediate step in manufacturing intermediate step in manufacturing silver halidessilver halides. .

► Silver halidesSilver halides (Permalink) (Permalink)The The lightlight sensitive ingredient in sensitive ingredient in photographphotographicic filmfilm and papers that is a combination of and papers that is a combination of silversilver with with bromine, fluorine, chlorine or bromine, fluorine, chlorine or iodineiodine. .

Exposed Exposed silver halidesilver halide particles form metallic particles form metallic silversilver that turns black when developed. that turns black when developed.

Potassium permanganatePotassium permanganate

► Structure:Structure:

The permanganate ion is tetrahedral.

Extraction from pyrolusite ore[MnOExtraction from pyrolusite ore[MnO22]]

Step 1:Step 1: Conversion of MnOConversion of MnO22 to potassium manganate(K to potassium manganate(K22MnOMnO44))

Pyrolusite fused with caustic potash or potassium carbonate in Pyrolusite fused with caustic potash or potassium carbonate in

presence of oxidizing agent like KNOpresence of oxidizing agent like KNO3.3.

KNOKNO33 KNO KNO22 + O + O

MnOMnO22 + 2KOH + O K + 2KOH + O K22MnOMnO44 + H + H22OO

MnOMnO22 + K + K22COCO33 + O K + O K22MnOMnO44 + CO + CO2 2

Step 2:Step 2: Oxidation of Oxidation of KK22MnOMnO44 to to KMnOKMnO44

The green mass of potassium manganate can be oxidised toThe green mass of potassium manganate can be oxidised to

potassium permanganate by treating it with water and COpotassium permanganate by treating it with water and CO22,,

ClCl22 or Ozone. or Ozone.,,

3K3K22MnOMnO44 + 2CO + 2CO22 2KMnO2KMnO44 +K+K22COCO3 3 + + MnOMnO22

2K2K22MnOMnO44 + Cl + Cl22 2KMnO2KMnO44 + 2KCl+ 2KCl

Oxidizing NatureOxidizing Nature► Oxidizing nature in acidic medium:Oxidizing nature in acidic medium:

2KMnO2KMnO4 4 ++ 3H3H22SOSO4 4 KK22SOSO4 4 ++ 2MnSO2MnSO4 4 + 3H+ 3H22O + 5[O]O + 5[O]

Eg. It oxidizes potassium iodide to iodineEg. It oxidizes potassium iodide to iodine

2KI + H2KI + H22SOSO4 4 + + O KO K22SOSO4 4 + H+ H22O + IO + I22 ] x 5 ] x 5

► Oxidizing nature in neutral or faintly Oxidizing nature in neutral or faintly medium:medium:

2KMnO2KMnO4 4 ++ HH22OO 2KOH2KOH ++ MnOMnO2 2 + 3[O]+ 3[O]

Eg. It oxidizes potassium iodide to iodatesEg. It oxidizes potassium iodide to iodates

KI + 3KI + 3 O KIOO KIO33