Free Chemistry NEET Notes for d-And-f Block Elements

Free Chemistry Notes for d-And-f Block Elements (NEET)

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- d-And-f Block Elements -

Important Chemistry Notes for IITJEE/NEET Preparation- d-And-f Block Elements

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d- AND f-BLOCK ELEMENTS

TRANSITION ELEMENTS

Elements where the last orbitals filled are the d orbitals known as transition elements. They have been placed in the middle of the periodic table between electropositive s-block and electronegative p-block elements.

GENERAL ELECTRONIC CONFIGURATION

Transition metals have the electronic configuration (n-1)d1-10ns0-2. When electrons fill orbitals, ns-orbital is filled first than (n-1)d-orbital.When losing during oxidation, ns electrons are lost first than (n-1)d electrons.

Zn ,Cd, Hg ,the end members of first three series have their general electronic configuration (n-1)d10ns2. These do not show properties of transition elements to any appreciable extent and are called non-typical transition elements.

CLASSIFICATION

Transition elements consist of the following four series

neet chemistry notes for d-and-f block elements class 12

ELECTRONIC CONFIGURATION OF TRANSITION ELEMENTS

PHYSICAL PROPERTIES OF TRANSITION ELEMENTS

METALLIC CHARACTER

Transition metals can lose valence electrons and form cations

They have simple hcp, ccp and bcc lattices characteristic of true metals. Except Hg, they are solids at room temperature and are dense (

in general, in case of osmium 22.6g/), lustrous, malleable, ductile thermal and electrical conductors. There is gradual decrease in electropositive character from left to right.

MELTING AND BOILING POINT

Due to strong metallic bond, they have high mpts and bpts. The mpts of these elements rise to a maximum and then fall with the increase in atomic number the manganese and technetium show abnormal values as shown by graph)

IONISATION ENERGY

The ionisation energy increases with the increase in the atomic number but not in regular manner. The ionisation energies of 5d elements are higher than those of 4 d and 3d elements due to greater effective nuclear charge which in turn is due to poor shielding of nucleus by 4f electrons.

Formation of

requires

and formation

requires

Hence Ni (II) compounds are thermodynamically more stable than Pt (II) Compounds.

Formation of

requires

and formation of

requires

Hence Pt (IV) compounds are relatively more stable than nickel (IV) compounds.

Thus

is well known where as the corresponding nickel compound is not known. (Ionisation energy graph is sketched here for ready reference)

ELECTRODE POTENTIAL

(

) (

) is governed by three factors

Heat of sublimation
Heat of ionisation
Heat of hydration

For the 3d transition metals the values are

V Cr Mn Fe Co Ni Cu

-1.18 -0.91 -1.18 -0.44 -0.28 -0.25 0.35 (Volts)

The irregular trend is due to variation in ionization energies and sublimation energies. Except copper 3d elements are good reducing agents but weaker than s-block elements.

OXIDATION STATES

In different types of compounds , transition metals exhibit different oxidation states. The highest oxidation state is exhibited in fluorides and oxides. In lower oxidation state the compounds formed are ionic and in higher oxidation state they are covalent in nature.

Osmium exhibit +8 O.S. (highest)often but Ru exhibit +8 oxidation state rarely. Transition metals also show oxidation states +1 and zero.

Fe3+ is more stable than Fe2+. Hence Fe2+ act as reducing agent Cr3+ is more stable than Cr2+. Hence Cr2+ act as reducing. Mn2+ is more stable than Mn3+ Hence Mn3+ act as oxidising agent

ATOMIC AND IONIC RADII

The values for atomic radii and ionic radii are in between the values for s and p-block elements. In 3d transition series the ionic radii for

ion decreases upto the middle of the period then becomes almost constant. Due to lanthanide contraction the second and third member of each group have atomic radii close to each other (Zr.160pm, Hf 159pm)

DENSITY

d-block elements have high density because of their small atomic sizes and strong metallic bonding.

Density Sc Ti V Cr Mn Fe Co Ni Cu Zn

g/ml 3.0 4.54 6.10 7.19 7.40 7.87 8.70 8.90 8.92 7 .13

ATOMIC VOLUME

Atomic volume decreases along the period due to decrease in size.

REACTIVITY

d-block elements are less reactive due to high ionisation energies. Some are almost inert and known as noble metals, e.g. Au, Pt, Ru, Rh, Os, Ir etc.

COMPLEX FORMATION

They are well known to form a large number of complex compounds mainly due to

Small atomic size and higher nuclear charge
Presence of partly filled or vacant orbitals
eg.

COLOURED IONS

The colour exhibited by transition metal ions is due to the presence of unpaired electrons in d-orbitals which permits the d-d excitation of electrons.

Colour of a complex depends on the metal, its oxidation state and its ligands. e.g.

[ Cu(H2O)4 ]2+ is Pale blue

[ Cu(NH3)4 ]2+ is Dark blue

CuSO4.5H2O is blue in colour and anhydrous CuSO4 is colourless.

In absence of ligands all d orbitals are degenerate (same energy) and the possibility of d-d excitation is no more.

In presence of ligand

have higher energy, d-d transition take place by absorption of light, hence the colour.

MAGNETIC PROPERTIES

Paramagnetic - This is due to the presence of unpaired electrons in d-orbitals. Paramagnetic character increases with the number of unpaired electrons.
Diamagnetic - Diamagnetic substances are repelled by an applied magnetic field.
Ferromagnetism - In this case permanent magnetic moment is acquired by substance e.g. Fe. Magnetic moment is given by B.M. where n = number of unpaired electrons and B.M. = Bohr magneton (unit of magnetic moment)

CATALYTIC PROPERTIES

The transition metals and their compounds behave as catalyst due to-

The presence of partly filled d-orbitals and exhibiting various oxidation states.
Their formation of intermediate complex with reactants and thus lowering the energy of activation
Their rough surface area provides active sites for adsorption of reactant molecules. eg.

Iron in the preparation of NH3 (Habers process)

Finely divided nickel for hydrogenation

Pt or V2O5 in the preparation of H2SO4 (Contact process)

Pt in the preparation of nitric acid (Ostwald’s process)

FORMATION OF ALLOYS

d block elements have a strong tendency to form alloys since their atomic sizes are very similar and in the crystal lattice one metal can be readily replaced by another. Alloys so formed are hard, have high m.pts. The metals Mo, W, Cr, Ni, and V are used for the production of stainless steel and alloy steel.

Amalgam is an alloy formed by mercury with other metals. Iron and platinum do not form any alloy with mercury.

INTERSTITIAL COMPOUNDS

The empty space present in a crystal lattice is known as interstitial place. The non metal atoms due to their small size (eg H, B, N, C etc.) when occupy such place the resulting compound is known interstitial compound. Such compounds are hard and rigid e.g. cast iron and steel.

NON STOICHIOMETRIC COMPOUNDS

The compounds not having the elements in the exact ratio as shown by the molecular formula are known as non stoichiometric compounds e.g., etc. In FeO the Fe:O is approx. 0.94:1 and not exactly 1:1.

IRON

OCCURRENCE

Being reactive in nature it does not occur in free state.

Ores of Iron-

Haematite
Magnetite
Limonite or hydrated ferric oxide
Iron pyrites
Siderite
Copper pyrites

EXTRACTION

It is extracted from haematite

in a blast furnace by reduction with carbon and carbon monoxide. The steps involved are-

Concentration - The crushed ore is agitated with water and then concentrated by electromagnetic method.
Roasting or Calcination - To remove volatile substances and organic matter.

Smelting - Roasted or calcinated ore is mixed with limestone and coke and fed into blast furnace. Reactions taking place in the blast furnace.

Lower region

Middle region

Upper region

The gases leaving the furnace contain CO and used to heat incoming air blast.The two layers in the blast furnace are-

Upper layer - Molten Iron - It is poured out in moulds and known as PIG IRON or CAST IRON.It contains 3-5% carbon and varying amounts of Mn, Si, P and S which make the iron hard and brittle.

Lower layer - Molten CaSiO3 (slag)

WROUGHT IRON

It is obtained by heating cast iron with haematite. The impurities are oxidised.

It contains carbon 0.2-0.5% and traces of P and Si. It is pure form of Iron and soft , malleable, ductile. It is used to make magnets in electric cranes and dynamos, railway carriage couplings being corrosion resistant.

STEEL

It contains carbon 0.1-1.5% and manufactured by following methods.

Bessemer process - Molten pig iron is heated in large pear shaped furnace lined with silica bricks at 1873K when impurities such as Mn, Si, C burn off. When all carbon is completely burn off the requisite amount of carbon is added.

Bessemer converter is lined with lime (CaO) or magnesia (MgO) when pig iron contains high percentage of phosphorous.

Open hearth process - The cast iron, scrap iron , haematite ore and lime are mixed together and melted in open hearth furnace lined with or calcined dolomite (MgO. CaO) depending upon the nature of impurities.

Electric furnace process - It is combination of Bessemer and open hearth process.

TYPES OF STEEL

Soft steel - contains carbon 0.25%
Mild steel - contains carbon 0.25-0.5%
Hard steel - contains carbon 0.5-1.5%
Alloy steel - contains varying percentage of Ni, Cr, Mn, Co,W, V e.g. stainless steel is an alloy of Fe, Cr and Ni.

HEAT TREATMENT OF STEEL
The hardness of steel depends on its carbon content and heat treatment.

Quenching - It involves the heating of steel to red hot (1123K) and cooling it by plunging into cold water or oil. It makes the steel hard and brittle.
Annealing - The steel is heated well below red heat and then cooled slowly. The steel becomes soft.
Tempering - In this process the quenched steel is reheated to 504 to 574K and allowed to cool slowly. The brittleness disappears and hardness is retained.
Nitriding - It involves the heating of steel in an atmosphere of ammonia when surface is coated with iron nitride. The steel becomes hard.
Case hardening -The steel is heated in charcoal and then quenched.The steel becomes hard.

ALLOYS OF STEEL
The important alloy steels are-

Name	Composition	Uses and Properties
Tungsten steel	Fe 94%, W 5%, C 1%	It is very hard, resistant to water and used for making Rock drills and Safeties
Stainless steel	Fe 73% Cr 18%, Ni 8%, C 1%	It is resistant to corrosion. Used for making cutlery
Manganese steel	Fe 86%, Mn 13%, C 1%	It is hard, used for manufacturing high speed cutting tools
Invar	Fe 64%, Ni 36%	It has small coefficient of expansion, used in watches, meter scales and pendulum rods
Permalloy	Fe 21%, Ni 78%, C 1%	It is strongly magnetised by electric current and lose magnetism when current is let off, used for manufacturing electromagnets and ocean cable.
Nickel steel	Fe 96-98%, Ni 2-4%	Resistant to corrosion, hard and elastic wire, used for making cables, gears and drive shafts.

SOME CHEMICAL PROPERTIES OF IRON

Red hot iron burns in O2 giving sparks

When steam is passed over red hot iron, hydrogen is liberated and magnetic oxide of iron (ferroso ferric oxide) is formed

Action of dil. H2SO4

Hot and conc. H2SO4

Action of dil. HNO3

PASSIVITY

The inertness exhibited by metals under conditions when chemical activity is to be expected is called passivity. Iron becomes passive with conc. HNO3, Chromic acid, conc. H2SO4 and KMnO4 etc. It is due to the formation of a thin layer of oxide at the surface of iron.

COMPOUNDS OF IRON

FERRIC CHLORIDE

PREPARATION

By passing dry chlorine over heated iron, anhydrous ferric chloride is obtained

By the action of hydrochloric acid on ferric hydroxide or ferric oxide

PROPERTIES

It is soluble in water, alcohol and ether. is yellow. Its aqueous solution is acidic. Sublimes at 300ºC, covalent and dissociates above 973K first into and e.g.

Action of heat

Oxidising nature of FeCl3 is shown by following reactions

STRUCTURE

USES

Used in medicine as ASTRINGENT and ANTISEPTIC. Its concentrated solution is used for etching copper and silver.

FERROUS SULPHATE (GREEN VITRIOL)

PREPARATION

Manufacture - From iron pyrites by oxidation by air

PROPERTIES

Hydrated is green and anhydrous is colourless.
Action of heat

Its aqueous solution is acidic due to cationic hydrolysis

Reducing nature - It is strong reducing is nature.

Addition compound with NO which is dark brown

USES

As mordant in dyeing, insecticide and in the preparation of Mohr’s salt.

FERROUS AMMONIUM SULPHATE (MOHR’S SALT)

PREPARATION
By mixing saturated solutions of

and cooling.

PROPERTIES
It is light green crystalline compound and does not effloresce.

FERRIC OXIDE

In nature it occurs as haematite.

Used in Bosch process as catalyst and polishing powder by jewellers and as red pigment.

IRON SULPHIDE FeS

By heating iron filings with dil. H2SO4

The reaction is carried out in Kipp’s apparatus. FeSO4 is obtained as by product H2S. Finds an extensive application in analytical chemistry. It has smell of rotten eggs.

COPPER

OCCURRENCE

It occurs in nature in large quantities in Michigan (USA).

Important ores are

Copper glance
Copper pyrites
Malachite
Cuprite (Ruby copper)
Azurite

PREPARATION

EXTRACTION

It is mainly extracted from copper pyrites.

CONCENTRATION

The ore is concentrated by froth floatation process.

ROASTING

The concentrated ore is strongly heated by hot blast of air on the hearth of reverberatory furnace. The following changes take place

SMELTING

The roasted ore is mixed with sand and heated in blast furnace.

The mixture of copper and iron sulphides melt together to form “matte”.

BESSEMERISATION

The molten matte mixed with little sand is poured into Bessemer converter. The following changes take place

The copper thus produced is called ‘blister copper’ and contains 2.0% impurities of Ag, Au, Ni, Zn, Pb, Sn, As, S etc.

REFINING

It is carried out by either of the following methods

By polling - The melt is stirred vigorously with green poles of wood and oxides are reduced by hydrocarbons emanating from wood.
Electrolytic refining of copper - Slabs of impure copper are made anode and thin sheets of pure copper as the cathode. Acidic copper sulphate is used as electrolyte.

The impurities like Zn, Fe, Ni,Co remain in solution being more electropositive in nature and Ag, Au, Pt, (less electropositive) collect below the anode in the form of anode mud or slime 99.99% pure copper is obtained. Anode mud provides about 25% of U.S. Silver production and 13% of U.S. gold production.

PROPERTIES OF COPPER

In aqueous solution it has two oxidation states +1 (cuprous) and +2 (cupric). Cu (I) salts tend to be white and insoluble in water while many salts of Cu (II) are water soluble however Cu(OH)2 is insoluble. CuS is one of the least soluble compounds.

Cu (I) disproportionates easily in aqueous solution.

Action of - It is attacked by first forming copper (I) oxide (Red) and then copper (II) oxide CuO (Black).
It forms a green layer of basic carbonate in presence of and moisture.

Not attacked by dilute acids e.g. HCl and but dissolves in these acids in presence of air.

COMPOUNDS OF COPPER

COPPER SULPHATE (BLUE VITRIOL OR NILA THOTHA)

PREPARATION

By dissolving Cu (II) oxide or carbonate in dilute.

From scrap copper

PROPERTIES

Blue crystalline compound.
Action of heat

Action of NH4OH

Tetrammine copper sulphate is known as SCHWITZER’S REAGENT. It is used to dissolve cellulose in the manufacture of artificial silk.

Action of KI

(It does not react with KCl, KBr or KF)

Action of potassium ferrocyanide

Action of KCN

Structure of

Four with cation and fifth with anion.

USES

In electroplating, as mordant in dyeing.

Bordeaux mixture (Mixture of

It is used as fungicide. In the preparation of Fehling solution and electric batteries.

CUPROUS CHLORIDE - COPPER (I) CHLORIDE

PREPARATION

It can be prepared from Cu alone or in combination with by action of concentrated hydrochloric acid.

By passing in a solution of

PROPERTIES

It is a white solid, almost insoluble in water.
Action of conc. HCl - It dissolves forming soluble complex.

On dilution white precipitate again appears.

Action of ammonia - It dissolves forming soluble complex

Action of acetylene - Red precipitate of cuprous acetylide is obtained.
With carbon monoxide it forms addition product.

With air - In air it is slowly oxidised to green basic cupric chloride.

With NaOH

With H2S

USES

In gas analysis for absorbing

and CO. In combination with

as catalyst for synthetic rubber.

CUPRIC CHLORIDE COPPER (II) CHLORIDE

PREPARATION

Form copper, cupric oxide or copper carbonate by the action of conc. HCl.

Anhydrous cupric chloride is prepared by burning copper in current of chlorine

PROPERTIES

Hydrated
Anhydrous
Aqueous dilute solution is blue due to complex
Concentrated solution is green due to complex
With Ammonia - First a precipitate which dissolves in excess of.

Action of heat
Hydrated salt on heating gives

STRUCTURE

CUPROUS OXIDE (RED OXIDE OF COPPER)

PREPARATION

When Fehling solution is reduced by glucose or aldehyde.

PROPERTIES

Red colour, insoluble in water. It forms stable complexes.

USES

In making ruby red glass and enamel.In manufacturing anti rust paints.

CUPRIC OXIDE (BLACK OXIDE OF COPPER)

PREPARATION

By heating malachite which is native copper carbonate.

PROPERTIES

Black powder reduced to metallic copper by

USES

In the manufacture of glass.It gives green colour to glazes and glass.

SILVER (Ag)

OCCURRENCE

It is found in nature and in combined state.

Principal ores are -

Argentite (silver glance)
Horn silver AgCl,
Pyrargyrite (ruby silver)

In small quantities in lead ,copper and zinc ores.

EXTRACTION

MAC ARTHER FOREST’S CYANIDE PROCESS

Concentration - Ore is concentrated by froth floatation process.
Treatment with NaCN - The powdered ore is treated with NaCN solution (0.7%) and air is bubbled through the mixture.

(a)

(b)

(c)

Reversible reaction is prevented by oxidation of

by air.

Precipitation of silver - It is done with zinc.

Refining
Electrolytic method

Anode - impure silver

Cathode - pure silver

Electrolyte -

SILVER FROM ARGENTIFEROUS LEAD (DESILVERISATION OF LEAD)

Lead, extracted from galena (PbS) contains small amount of silver and is called argentiferous lead. Silver is recovered from it by-

Parke’s process - Molten argentiferous lead is shaken with zinc when whole of silver passes into zinc. On cooling Ag- Zn alloy solidifies and being lighter floats over molten lead. It is separated, melted and distilled. Zinc distills over and silver is left behind. Success of the method depends upon the fact that-

(a) Silver is more soluble in molten zinc and

(b) Molten Zn and lead are immiscible

Pattison’s process - (When silver is less than 1.0%).The lead-silver mixture containing 2.6%. Silver melts at lower temperature than pure lead. When molten argentiferous lead is allowed to cool pure lead solidifies first and removed. The silver content of the mixture is allowed to raise to 2.6%.The silver is then recovered by cupellation.

PROPERTIES

It is a noble metal not attacked by atmospheric oxygen. The surface is tarnished due to formation of Ag2S due to H2S present in air.

Dissolves in dilute and concentrated nitric acid

Dissolves in alkali cyanide

Dissolves in conc. sulphuric acid (not in dil. sulphuric acid)

USES

For making ornaments (80%Ag+20%Cu), electroplating, preparation of mirrors.

Fineness of Silver - It is the amount of silver present in 1000 parts of silver alloy. 925 fine silver means an alloy of 92.5% silver and 7.5%copper.

COMPOUNDS OF SILVER

SILVER NITRATE OR LUNAR CAUSTIC

PREPARATION

By the action of dilute nitric acid on silver.

PROPERTIES

It is colourless crystalline solid, soluble in water. It leaves black deposit when rubbed on the skin due to formation of finely divided silver.
Action of heat

Tollen’s reagent - The ammoniacal silver nitrate solution is known as Tollen’s reagent.

Reaction with aqueous solution of certain compounds

USES

For silvering mirror ,electroplating, in medicines, for the preparation of silver halides used in photography. Particularly AgBr which is most sensitive to light.

GOLD (Au)

OCCURRENCE

It occurs free as Reef gold, Vein gold or auriferous quartz. Some improtant ores are

Claverite ,
Sylvanite
Auriferous pyrites. These are sulphide ores of Cu, Ag, lead which contain gold.

EXTRACTION

By cyanide or Mac Arther Forest cyanide process

CONCENTRATION
Sulphides and tellurides are concentrated by froth floatation process.

ROASTING

The concentrated ore is roasted to remove oxidisable impurities of Te, As and S.

Formation of complex- NaCN solution is sprayed over the crushed ore and the gold with air, forming complex ion in solution.

The gold is then recovered as a solid by reduction.

PARTING

Removal of impurities of Ag and Cu from gold is known as parting.Impure gold is boiled with conc. when Ag and Cu dissolve and Au remains unaffected

PURIFICATION

By electrolytic method using gold chloride 2.5-6.0% and conc. HCl.·

Plattner chlorine extraction process (From auriferous pyrites)
The moistened auriferous pyrites is saturated with chlorine, leached with water then treated with which precipitates gold.
Auriferous pyrites (moistened)

Impurities of Ag and Cu are removed by parting (as above).

PROPERTIES

Pure gold is soft, hardened by Ag or Cu.

Fineness of gold - It is expressed in terms of carats. Pure gold is 24 carats. 22 carats mean it contains 22 parts by weight of gold and 2 parts by weight of other metals generally copper.

It is very inert and not attacked by oxygen, water and acids.
It is attacked by aqua regia

It is attacked by chlorine.

Auric chloride forms red crystals. Soluble in water and decomposed on heating.

ZINC (Zn)

OCCURRENCE

It is not found free in nature.The principal ores are -

Zinc blende (sphalerite) ZnS
Zincite or Red zinc oxide ZnO
Franklinite
Calamine or Zinc spar
Willemite

PREPARATION

EXTRACTION
It is extracted by reduction process from ZnS (Zinc blende).

CONCENTRATION
The ore is concentrated by froth flotation process.

ROASTING
The concentrated Zinc blende is roasted in a current of air.

(is utilised for the manufacturing of H2SO4)

If calamine ore is used, it is calcined.

REDUCTION

The ZnO is reduced by mixing with carbon and heating in fire clay retort.

PURIFICATION

Zinc so obtained contains the impurities of Fe, Pb, Cd, As or Sb. It is purified by

Distillation or
Electrolytic method

Anode impure :

Cathode pure :

Electrolyte : Acidic solution of

Liquation - Molten Zn is allowed to flow down on sloping hearth when non fusible impurities are left behind.

Electrolytic method – Pure

is electrolysed when Zn is deposited on aluminium cathode. It is scraped off and melted to obtain 99.95% pure metal.

Zinc dust - It is prepared by atomising molten zinc with blast of air.

Granulated Zinc - It is prepared by pouring molten Zinc into cold water.

PHYSICAL PROPERTIES

It is bluish white metal, stable in air.
In moist air a protective covering of basic zinc carbonate is formed at its surface
Action of heat - When heated to 500ºC it catches fire with bluish white flames forming ZnO which is very light and called philosopher's wool.

CHEMICAL PROPERTIES

Action with acids

Displacement reactions

With non metals

It is powerful reducing in nature.

USES

Galvanising, sherardizing, in Parke’s process for desilverisation of lead , for extraction of Ag and Au (Cyanide process). Zinc compounds are used in paints, filling rubber etc.

COMPOUNDS OF ZINC

ZINC OXIDE, PHILOSOPHER'S WOOL, ZINC WHITE OR CHINESE WHITE, ZnO

PREPARATION

PROPERTIES

It is white powder becomes yellow on heating but again white on cooling.
It sublimes at 673K.
With alkali - It forms zincate.

Reduction

Dissolves in acids to form corresponding salts.

USES

As a white paint , in medicines, glaze in ceramics and filler in rubber industry.

WHITE VITRIOL

PREPARATION

By the action of dil. on Zinc metal, ZnO or

PROPERTIES

Colourless, crystalline compound, highly soluble in water.
Action of heat

USES

It is used to prepare lithophone

white pigment , galvanising iron and steel, as mordant in calico printing, in medicine as eye lotion.

ZINC(II) CHLORIDE

PREPARATION

It is prepared by the action of dilute HCl on Zn, ZnO or ZnCO3

PROPERTIES

It is very deliquescent, soluble in water and organic solvents.

Anhydrous zinc chloride

USES

As timber preservative, flux in soldering, preparation of vulcanised paper and fibre.

MERCURY (Hg)

OCCURRENCE

It occurs in free state as small quantities. Its chief ore is -

Cinnabar HgS
Tiemannite
Calomel Hg2Cl2

EXTRACTION

Concentration - Cinnabar ore is concentrated by froth floatation process.
Roasting - Roasting is carried out in a shaft furnace when mercury is obtained by auto reduction.

Roasting may be carried out with iron scrap or quicklime.

Purification - It contains the impurities of Zn, Pb, Sn or Bi. Some of these impurities get oxidised in air and form a black scum on the surface. Finally it is purified by distillation in vacuum.

PROPERTIES

Physical properties - It is silvery white liquid also known as Quick silver or live silver. It is the heaviest liquid known. Sp. gr. 13.59 at.
Action of air - It is not attacked by air either dry or moist at ordinary temperature.
It forms mercuric oxide at.

Dilute acids have no action on mercury except dil..

With concentrated acids

Deadening of Hg - On Shaking vigorously alone or with fats or sugar it changes to grey powder. This is called deadening of mercury.
Tailing of mercury - In presence of ozone it loses its meniscus which is known as tailing of mercury.
Amalgams - The alloys of mercury with metals excerpts (Fe and Pt) are commonly known as amalgams.
Ammonium amalgam - Sodium amalgam when placed in conc. solution of , there is swelling and butter like mass is formed which is ammonium amalgam.
Mercury tree - When small amount of Hg is poured into solution . (Ag-Hg) is formed which grows like a tree and called mercury tree.

USES

In thermometers , barometers, electric cells etc.

COMPOUNDS OF MERCURY

MERCURIC OXIDES HgO

PREPARATION

By heating mercury in air or O2

By heating mercuric nitrate

From mercuric chloride by the action of NaOH

Red HgO and yellow HgO differ in their particle size.

On heating yellow form changes to red.

USES

It is used as pigment in oil paints and as mild antiseptic in ointments.

MERCUROUS CHLORIDE OR CALOMEL

PREPARATION

From mercurous nitrate

From mercuric chloride by action of mercury

PROPERTIES

It is insoluble in water purified by sublimation.
Action of NH3 - It becomes black with ammonia.

Action of heat - It is decomposed.

USES

In ceramics for golden colour and as calomel electrode.

MERCURIC CHLORIDE OR CORROSIVE SUBLIMATE

PREPARATION

By heating mercury in a current of chlorine.

MANUFACTURE

By heating mercuric sulphate with equal quantity of sodium chloride.

PROPERTIES

Colourless, crystalline substance, covalent in nature and gives 5-8% solution in water.
With SnCl2 - It is reduced to mercury

With KI - It gives scarlet precipitate soluble in excess of KI.

With NaOH - It gives HgO.

Nessler’s reagent - An alkaline solution of is known as Nessler’s reagent. It is used for the identification of ammonia and ammonia salts.

Brown (iodide of Millon’s base)

MERCURIC IODIDE

PREPARATION
By adding KI solution to any mercuric salt solution.

PROPERTIES
Scarlet

It is soluble in excess of KI forming complex ion. Its alkaline solution is Nessler’s reagent as shown above.

MERCURIC SULPHATE

PREPARATION
By treating Hg with conc.

PROPERTIES
It is white opaque mass, decomposes on heating to gives Hg (I) Sulphate.

COMPOUNDS OF MANGANESE

POTASSIUM PERMANGANATE

PREPARATION

On large scale it is prepared from

pyrolusite. The steps involved are as follows

Preparation of potassium manganate - By fusing manganese dioxides with.

Oxidation of

solution is either added

H2SO4 or

(The last oxidation is known as STADELER ‘s process)

Electrolytic oxidation - Nowadays electrolytic oxidation is prefered. The manganate solution is electrolysed between iron electrodes separated by diaphragm.

At anode

At cathode

PHYSICAL PROPERTIES
It is dark purple solid, soluble in water giving purple solution. Its melting point is 523 K.

CHEMICAL PROPERTIES

Action of heat -
Oxidising nature - It is strong oxidising agent , both in alkali as well as in acidic medium and also in neutral.

In acidic medium

In alkaline medium

In neutral medium

In alkaline medium it oxides potassium iodide to potassium iodate and nitro toluene to nitro benzoic acid.

Action of hydrogen - It burns on heating in a current of.

Equivalent weight of in different medium

Equivalent weight in acid medium
Equivalent weight in alkaline medium
Equivalent weight in neutral medium

(See ionic equations above)

USES

As oxidising agent, disinfectant, 1% alkaline solution of KMnO4 is used to test unsaturation in organic compounds under the name of Baeyer’s reagent. It is used for the volumetric estimation of Fe++ salts,oxalic acid etc.

COMPOUNDS OF CHROMIUM

POTASSIUM DICHROMATE

PREPARATION

It is manufactured from chromite ore

The steps involved are -

Preparation of sodium dichromate - Finely powdered chromite is mixed with soda ash and quick lime and roasted in reverberatory furnace or rotary furnace in excess of air.

Chromite can be fused with molten alkali in presence of air.

The solution is filtered and acidified with dil. H2SO4 when sodium dichromate is obtained.

Conversion of sodium dichromate to potassium dichromate.

Hot concentrated solution of Potassium dichromate

is less soluble and separates out on crystallisation.

PROPERTIES

It is garnet red prismatic (orange) crystalline compound having melting point 398°C. Soluble in water.

CHEMICAL PROPERTIES

Action of heat

Action of cold

Action of alkali

Oxidising nature - It is powerful oxidising in nature.

Formation of chromyl chloride - When a chloride is heated with potassium dichromate and conc. orange red vapour of chromyl chloride are formed.

With lead salts it gives insoluble chromate salt.

USES

In chrome tanning
In dyeing-calico printing
In photography
Chromic acid used as cleaning agent,
In preparation of compounds such as etc.

STRUCTURE

It consists of two tetrahedra with common oxygen atom

Dichromate ion

Structure of chromate ion : It has tetrahedral structure

At pH about 4 dichromate ion (

) and chromate ion (

) exist in equilibrium. These are interconvertible.

INNER TRANSITION ELEMENTS

The elements in which the filling of atomic orbitals by electrons take place in f subshells, two levels inside the outer subshell, are known as inner transition elements. Thus these elements form a series within the transition series. They are also known as f- block elements since the differentiating electron enters the f -subshell.

CLASSIFICATION OF F-BLOCK ELEMENTS

They have been classified into two series.

4f-series (first inner transition series) - The differentiating electron enters in 4 f orbitals. The elements belonging to this series are also known as Lanthanides or Lanthanones.
5f -series (second inner transition series) -The differentiating electron enters in 5 f orbitals. The elements belonging to this series are also known as Actinides or Actinones.

For the sake of symmetry of the periodic table they have been placed outside the periodic table.

LANTHANIDES

The fifteen elements from lanthanum (At. no. 57) to lutetium (At. no. 71) are known as lanthanides or rare earths (because they were obtained as earths (oxides) from relatively rare minerals).

PROPERTIES

ELECTRONIC CONFIGURATION

The general electronic configuration of these elements is

The lanthanum electronic configuration

and lutetium electronic configuration

, have no partially filled 4 f orbital in their ground state, are considered as lanthanides due to their properties close to these elements.

OXIDATION STATE

The common oxidation state of lanthanides is +3 but some elements also exhibit +2 and +4 oxidation states in which they leave behind stable ions eg.

An aqueous solution of is a good oxidising agent. The

and

can exist in aqueous solution and are good reducing agents. But there are exceptions also e.g.

MAGNETIC PROPERTIES

Magnetic properties have spin and orbit contributions (Contrast “spin only”of transition metals). Hence magnetic momentums are given by the formula.

where L = Orbital quantum number, S = Spin quantum number

All lanthanide ions with the exception of

are paramagnetic in nature. The trend in magnetic moment is shown by graph.

LANTHANIDE CONTRACTION

There is a steady decrease in the radii as the atomic number of the lanthanide elements increases. For every additional proton added in nucleus the corresponding electron goes to subshell. The shape of f -orbitals is very much diffused and they have poor shielding effect. The effective nuclear charge increases which causes the contraction in the size of electron charge cloud. This contraction in size is quite regular and known as Lanthanide contraction.

Consequences of lanthanide contraction

Covalent character of cations increase.
Electronegativity - The electronegativity of trivalent ions increase slightly.
Basicity - There is decrease in basic strength of oxides and hydroxides.
Eo value - There is small increase in standard electrode potential values.

COLOUR

The species containing unpaired electrons are coloured and so is the case with lanthanide ions. The f-f transitions are possible due to absorption of light from the visible region.

MELTING AND BOILING POINT

Lanthanides have high melting and boiling points but there is no regular trend.

DENSITY

Lanthanides have densities varying from. But there is no definite trend for these values.

ELECTRONEGATIVITY
Electronegativity values of lanthanides are almost same as that of s-block elements. Lanthanides form ionic compounds.

IONISATION ENERGIES
The ionisation energy values of lanthanides are not very high due to their large size and are comparable with those of alkaline earth metals.

COMPLEX COMPOUND

Due to having large ionic size they have little tendency to form complexes.

REACTIVITY

Due to their low values of ionisation energies the lanthanides are very reactive.

ALLOYS

They form alloy especially with iron e.g. MISCH METAL rare earths

ACTINIDES

The fifteen elements from actinium (At. no. 89) to lawrencium (At. no. 103) are known as actinides and constitute the 5f. Series. From neptunium to onwards the elements are man made (artificially prepared) and also known as transuranium elements.

PROPERTIES

ELECTRONIC CONFIGURATION

The differentiating electron enters the 5f atomic orbital. Their general electronic configuration is

Since there is not much difference between 5f and 6d, it is difficult to predict whether the electron has entered 5f or 6d.

OXIDATION STATE

The common oxidation state is +3 but other oxidation states are also exhibited by actinides the maximum being +7.

MAGNETIC PROPERTIES

The magnetic moments of actinide ions are smaller than theoretical values.
It is hard to interpret due to large spin orbit coupling.

ACTINIDE CONTRACTION

It is similar to lanthanide contraction due to poor shielding of electrons.

MELTING AND BOILING POINTS

They have high values for melting and boiling points but there is no regular trend.

DENSITY

The value of density vary from 7.0 gcm–3 to 19.84 gcm–3. Again there is no regular trend.

REDUCING CHARACTER

They are strong reducing agents as they have high values approximately 2.0 volts.

REACTIVITY

Actinides are very reactive in nature and combine with oxygen and halogens like lanthanides.

COLOURED IONS

Actinide ions are coloured due to the presence of unpaired electrons and transitions.

COMPLEX FORMATION

They have higher tendency to form complex compounds.