Transition Elements Chapter 1 PDF

Transition elements BY DR EMAD AGWA Where it exist ? why so called ? We have more than 60 transition elements which exist in 1- D-BLOCK main transition 2- F-BLOCK inner transition the transition metals they called so since they are a...

Transition elements BY DR EMAD AGWA Where it exist ? why so called ? We have more than 60 transition elements which exist in 1- D-BLOCK main transition 2- F-BLOCK inner transition the transition metals they called so since they are a mid-way between the stable representative elements and the unstable radioactive elements show great similarities within a given period as well as within a given vertical group  They contain the elements with electrons occupying the d sublevel  Ten groups /4 periods According to period they can be classified to 1- first transition series (3d) 2-second transition series (4d) 3- third transition series ( 5d) 4-fourth transition excluding mercury which is considered from lanthanides.  characteristics  The first column take the address 3B  Second takes 4B and so on till reaching 7B  Afterthat groups 8, 9, 10 takes the same number which is 8B ??? This is due to the great cross similarity between them is more in periods than between elements in vertical column  In the previous pic. Why zinc solution was colorless  What must the charge be on a Fe ion that is isoelectronic with Co+3? First transition  Scandium most of its This is not a rare compounds surprising color element that being and magnetism of transition metal exists in colorless and compounds usually compounds diamagnetic. arise from the d mainly in the electrons on the +3 oxidation metal ion, and Sc state +3 has no d eg ScCl3, electrons. Sc2O3, ADDITION OF SCANDIUM TO ADDED TO MERCURY ALUMINUM TO PRODUCE A VAPOR LAMP TO PRODUCE LIGHT AND HARD ALLOY TO STRONG ILLUMINATION BE USED IN MIG FIGHTER USED IN NIGHT TV PHOTOGRAPHY (DAY LIGHT)  the Titanium resistance of dioxide, or more titanium to correctly, 2- titanium Because of its chemical titanium(IV) relatively low attack makes oxide (TiO2), is a density and high highly opaque it a useful strength, titanium substance used material for is an excellent as the white structural material, pipes, pigment especially in jet pumps, and cosmetics engines.(high reaction (sunscreens) due durability) vessels in to its minute the chemical nano particles industry. (UV).  3-vanadium  Used mostly in alloys with other metals such as iron (80% of vanadium is used in steel). corrosion resistant.  Ferrovanadium alloy is very hard used in car spring manufactutre  Vanadium(V) oxide (V2O5) is used as an industrial catalyst in the production of materials such as sulfuric acid  The principal oxidation state of vanadium is 5+  4-chromium can be added directly to iron in the steelmaking process.(stainless steel) (ferrochrome alloy) Chromium metal, which is often used to plate steel, is hard and maintains a bright surface by developing a tough invisible oxide coating. Why ??? Although reactive but it resist oxidation ? Why ?  Sincethe formed oxide layer is non-porous and resist further oxidation to other layers of chrome  The chromium(VI) species are excellent oxidizing agents, especially in acidic solution ((Cr2O7 )-2 where chromium(VI) as the dichromate ion is reduced to the Cr3+ ion(green color)  Cr2O3 used in dyes manufacturing 5- manganese The most common use of manganese is in the production of an especially hard steel used for rock crushers, bank vaults, and armor ‫ درع‬plate  Aluminum-manganese alloy is used in manufacturing of cans used for soft drinks ? Since it is highly resistant to corrosion.  Manganese can exist in all oxidation states from +2 to +7, although +2 and +7 are the most common.  MnO2 is strong oxidizing agent used in dry cells  Potassium permanganate KMnO4 strong oxidizing agent (Purple color) used as antiseptic , in skin diseases  Manganese sulphate MnSO4 is used as topical fungicide 1/8000  6- iron 25 The chemistry of iron mainly involves its +2 and +3 oxidation states  Used in knives , electric pylons ‫ ابراج الكهرباء‬, guns and cannons , reinforced concretes  As catalyst in industrial preparation as in 1- ammonia preparation (haber-bosch method) 2-conversion of water gas to liquid fuel (fischer- tropsch method) (water has a mixture of CO and H2)  7- COBALT 27  Thechemistry of cobalt involves mainly its +2 and +3 oxidation states  Canbe magnetized as iron can be used in battery manufacturing in cars  Has 12 isotopes the most important of the is Co-60 Which emits gamma ray , used in 1- preservation of food 2- detecting quality of industrial product 3- detecting problems in operation process as cracks and loose welded connections 4- medicine , diagnosis and treatments 8- nickel 28 Nickel in compounds is almost exclusively in the +2 oxidation state  Nickelis also widely used in the production of alloys such as steel which resist corrosion and strong acids  Actas a catalyst , in hydrogenation of plants oil to produce artificial fats Nickel- chrome alloy Used to plate Used in used in making other metal ‫تنكيل‬ heating coils and manufacturing of ‫المعادن‬ nickel-cadmium electric furnaces because it resist because it protect battery which is corrosion even at other metals from corrosion and rechargeable high temperature produce elegant appearance 9- copper The chemistry of copper principally involves the +2 oxidation state, but many compounds containing copper(I) are also known. Aqueous solutions of copper(II) salts are a characteristic bright blue color Used in manufacturing of electric cables and coins Copper sulphate CuSO4 USED as 1- Insecticide 2- fungicide 3- water purification 4- making Fehling's solution Fehling's solution used to detect glucose in diabetic patient (old methods) Copper-tin alloy (Cu-Sn) known as bronze Copper-zinc (Cu-Zn) known as brass used in plating steel Zinc Zinc is a white, lustrous, very active metal that behaves as an excellent reducing agent  About 90% of the zinc produced is used for galvanizing steel.  Zinc forms colorless salts in the +2 oxidation  ZnO is used in cosmetics , rubber , paints  ZnS is used in illuminating paints and X-ray screens  Open discussion 1- why element like chrome and copper show abnormality or deviation from hund’s rule 2- why it is difficult to get C0+5 3- why it is easily to get iron (lll) from iron (ll) and it is difficult to get manganese (lll) from manganese(ll) It is all about extra stability offered by half filled or completely filled 3d orbital Element of 3d start to lose electron from 4s before 3d All elements has oxidation number +2 except Sc scandium which has +3 only Manganese has the greatest oxidation number +7 while the lowest oxidation number is shown in copper +1 ,+2 The maximum oxidation number do not exceed the gp number except group 1B (Copper group)  On contrary to rep elements , transition elements has more than one oxidation number  since there is just gradual increase in ionization energies in transition metals from one number to another while there is a great jump in rep elements Definition of transition elements  They are elements that have incompletely filled d or f sublevel , whether in atomic state or in one of its compounds.(oxidation state)  This is why Cu , Ag , Au is considered as transition  elements, while Zn, Cd , Hg is not considered as transition elements.  Write electron configurations for each of the following. A. Cr, Cr+2, Cr+3 b. Cu, Cu+ c. V, V+2, V+3 General properties 1- atomic mass : increases gradually except for nickel which has 5 isotopes there average mass number is 58.7 amu 2- Atomic radius Decreases slightly from Sc to Cr , due to increased Zeff, Then remains nearly constant till copper as gradual addition of electrons to d sublevel causes increased repulsion which overcomes the increased attraction of Zeff But generally speaking they are almost the same size and this is why they are used in alloys manufacturing 3- metallic properties All are shiny metals , good conductor of heat and electricity. 4- boiling point High , due to strong metallic bond (both electrons in s and d orbitals) so they shows better electric conductivity than metals of rep elements 5- density D= M/V SO density increase when moving from left to right (from Sc to Cu)  6- chemical activity it differs depending on many factors as electronegativity , e affinity , size ,….etc Some are of low reactivity Cu Some has intermediate reactivity Fe Some are highly reactive Sc 7-magnetic properties (imp) elements are generally classified acc to their magnetic properties to a- paramagnetic : elements which is attracted to external magnet This is due to presence of unpaired electron/s in the 3 d sublevel , such electron spins creating certain magnetic field in certain direction and hence can be attracted to external magnet  B- diamagnetic elements which is repelled from external magnet since all the d orbital’s electrons are paired. (2 magnetic field in opposite directions omits each others)  (5) Question: Why does the number of oxidation states for transition metals increase in the  middle of the group?  Answer: Due to increase in the number of unpaired electron in the d orbital, the oxidation states for transition metals increase in the middle of the group.  (6) Question: What two transition metals have only one oxidation state?  Answer: Scandium and Zinc What is meant by magnetic moment?  Itis the tendency degree of an element to be attracted to magnetic field.  Itis determined by the no. of unpaired electrons in the 3d level.  Why zinc has magnetic moment zero ?  Which of the following is paramagnetic/mention the magnetic moment Fe , Cr , Cu , Cu in CuSO4  8-COLOR OF IONS white light/7colors , when it falls on transition element , the transition element absorbs only certain color and reflect the remaining , the reflected color called complementary colors  theabsorption of certain color depend on presence of unpaired electrons and its number , which is excited by certain color frequency and reflect the complementary ones  So some ions of such group is colorless as ……… and …………  For complementary colors  9-catalytic activity catalyst is the substance that increase the speed of the reaction without being consumed or chemically affected after the reaction.  Catalyst  decrease the energy need for the reaction. Metals of first transition are excellent catalyst because they have unpaired electrons which form weak bonds between reactant molecules increasing there concentration in over its surface area, thus increasing velocity of the reaction.  Examples  1-finely divided iron as a catalyst in industrial preparation of ammonia (HABER-BOSCH) N2 + 3H2 Fe/ 500 C/200 ATM NH3  V2O5 in industrial preparation of sulphuric acid. (CONTACT PROCESS) 2 SO2 + O2 V2O5/450 C 2SO3 SO3 + H2O H2SO4 3-finely divided nickel in saturation (hydrogenation) of plant oil to produce artificial fat (margarine)  4- manganese dioxide(MnO2) in decomposition of hydrogen peroxide 2H2O2 Mno2 2H20 + O2  The catalyst decreases activation energy as shown in graph  Iron  4th abundant element in earths crust  Usually found as oxide in its ore  Rarely as elementals as in meteorite (90% pure iron)  Usually the iron oxide is found mixed with many impurities as sulphur , phosphorous.  The common oxides called magnetite , hematite , limonite , siderite  Iron production  Iron production is giant industry that requires money and effort , capabilities evaluation of iron ore , to decide to extract or not This process depend on 1- % of iron in the ore 2- % of impurities 3- the ease of removal of that impurities 4- the type of impurities (sulphur, phosphorous arsenic , ……..etc )  1st stage ore dressing for a- improving physical properties of the ore b- improve chemical 2 stage reduction properties nd of the ore extraction to get rid of oxygen , some process impurities done in blast furnace or midrex furnace 3- 3rd stage iron production complete removal of impurities and addition of some substance to produces required steel  1- ore dressing to concentrate the ore to get rid of many impurities to make it ready for next step this process takes place in 4 steps for (physical improvements ) 3 steps 1- crushing 2- sintering 3- concentration 1- crushing ‫الطحن‬ to break big parts to smaller one , to facilitate removal of impurities (becomes more exposed due to increased SA) 2- sintering ‫تكليس‬ to collect fine parts together to form bigger ones so that it would be homogenous and suitable for use in the blast furnace. 3- concentration ‫تركيز‬ done to remove most of impurities by several physical, mechanical methods as a- magnets b- electricity c- surface tension to increase the concentration of the iron ore  The 4th process is chemical one done to improve the chemical properties of iron , it is called roasting ‫تحميص‬ heating the ore strongly in air for two reasons  1- increase the iron percentage % by getting rid of both humidity (H2O) , and CO2 FOR LIMONITE 2Fe2O3.3H2O ∆ 2Fe2O3 + 3H2O FOR SIDERITE FeCO3 ∆ FeO + CO2 FeO + 1/2O2 ∆ Fe2O3  For the last two reactions , does the iron concentration really increased ??  WHICH IS ESY TO OBTAIN FeO or Fe2O3  2-The second reason for heating in air is to oxidize some remaining impurities as sulphur and phosphorous S + O2 ∆ SO2 4P + 5O2 ∆ 2P2O5  2- reduction (2nd stage)  Takes place in special furnace as a-blast or high furnace ‫الفرن العالي‬ The reducing agent used in (CO) CO is a good reducing agent since it is unstable and requires oxygen so it takes oxygen from metal oxides less active than it as follow Fe2O3 + 3CO 2Fe + 3CO2  How to produce (CO) BY burning of coke‫( فحم حجري‬carbon) , which initially will produce carbon dioxide. C + O2 ∆ CO2  Inpresence of excess carbon it react with carbon dioxide to produce carbon monoxide CO2 + C 2 CO   For midrex furnace , what is the reducing agent  The reducing agent called water gasit is a mixture of (CO + H2)  Water gas is produced from methane ‫الطريقة دي مناسبه للبالد الغنية بالغاز الطبيعي‬ 2CH4 + CO2 + H2O 3CO + 5H2 2Fe2O3 + 3CO + 3H2 4Fe + 3CO2 + 3H2O 2- Iron is present in the earth’s crust in many types of minerals. The iron oxide minerals are hematite (Fe2O3) and magnetite (Fe3O4). What is the oxidation state of iron in each mineral?  3) 3rd stage iron production  Involve producing diff. types of iron  Steelproduction depend on 1- removal of residual impurities 2- addition of some elements to produce the required steel  Furnacesused are 1- oxygen converter 2- open hearth furnace 3- electric furnace  Alloys‫السبائك‬  Itis the combination of metal with other metal or even non-metal to produce an alloy of better properties.  Why we prefer using alloys in industry , life , …etc since the alloy posses better and enhanced properties rather than the pure metal enhanced properties as 1- resist corrosion 2-higher melting point 3- more shiny 4- more stronger  Preparation of alloys  1-melting by melting metals together then leaving the mixture to cool.  2-electric deposition (electroplating ) ‫الطالء‬ plating a metal is allowing other metal atom to be deposited on its surface eg ferronickel alloy ‫زي نواكل العربيات‬ resist corrosion and add shiny appearance Types of alloys 3 types of alloys 1- interstitial 2- substitutional 3- inter-metallic alloy 1- interstitial In this types an introduction of element of smaller size than the pure metal The newly introduced metal atom occupy the intermolecular space of the pure element Such type causes a new alloy of increased hardness , different physical properties as malleability , ductility , melting point. Example of this alloy is steel (iron-carbon) Hardness due to prevention of slipping of layers of metal one upon another  2- substitutional  Inthis type pure metal atoms is substituted by atoms of other metal of same 1- atomic radius 2-crystal lattice 3-chemical properties  Example 1- stainless steel (ferrochrome alloy) 2- ferronickel alloy 3- copper-gold alloy  3- inter-metallic alloy  Inthis type chemical reaction between the two elements to form the alloy  The chemical formula of the newly formed alloy do not obey valence law Examples 1- aluminum-nickel and aluminum copper (called duer aluminum alloy) 2- cementite ( Fe3C) 3-lead-gold alloy (Au2Pb)  Iron  Physical properties 1-malleable and ductile 2- soft , low hardness 3-paramagnetic 4-high density (7.86 g/cm3 ) 5-high melting point 1538 c  Chemical properties oxidation number mainly involves two states. a- +2 losses 2 electrons from 4s b +3 losses 2e from 4s and 1e from 3d  Chemical reactions of iron  1-dry air only by excessive heating so only red hot iron react with air 3Fe + 2O2 Fe3O4  2-effect of water vapor only red hot iron react to produce Fe3O4 3Fe + 4H2O Fe3O4 + 4H2  3- reaction with non-metals classic reaction that produce salt A- HOT iron filling react with chlorine to produce FeCl3 and not feCl2 2 Fe + 3Cl2 2FeCl3 B- reaction with sulphur to produce iron(ll) sulphide Fe + S FeS Chlorine is stronger oxidizing agent than sulphur   reaction with ACIDS  Usually metal try to replace hydrogen in the acids a- with dilute acids  iron is more active than hydrogen so it replace it in diluted ACIDS forming salts of iron(ll) Fe + H2SO4 / dil FeSO4 + H2 Fe + 2HCL /dil FeCl2 +H2 The question is WHY iron in its reaction sometimes produces iron ll and in other reactions produces iron lll ?  First of all we always refer to iron ll as ferrous and iron lll as ferric Iron prefers to exist in the +3 state due to being in the half filled state of 3d Some times the reaction condition or products prevent further oxidation to produce ferric ion H2 released in the previous reactions is a powerful reducing agent so it prevent further oxidation of ferrous to ferric so to get FeCl3 you must react hot iron with chlorine gas  B- with concentrated acids with sulphuric acids it produce mixture of ferrous and ferric sulphate and sulphur dioxide and water  3Fe + 8H2SO4 /C FeSO4+ Fe2(SO4)3+ 4SO2+ 8H2O  IRON Does not react with conc. HNO3 , due to passivity of iron ? Formation of complete non-porous layer of oxide over iron surface preventing it from further reaction  Removal of such layer by either scratching or using dil HCl  Iron oxides  1- FeO (iron ll oxide) (ferrous oxide) 2- Fe2O3 (iron lll oxide ) ferric oxide  3-Fe3O4 (magnetic iron oxide)  Note increase in oxygen content from one iron form to another is called oxidation and the reverse is reduction  FeO Fe2O3 ( oxidn) (1:1) (2:3) Fe2O3 FeO (redn) (2:3) (1:1)  1- FeO (iron ll oxide) (ferrous oxide)  Preparation by heating iron oxalate in absence of air.  In this reaction the product is (iron ll oxide - ferrous oxide) not iron lll oxide only if no air  since CO is produced too which is a powerful reducing agent , prevent further oxidation of iron ll to iron lll  by reduction of higher oxides by reducing agent as H2 gas , or CO  Fe2O3 + H2 400 – 700 C 2FeO + H2O  Fe3O4 + H2 400 – 700C 3FeO + H2O Properties Black , solid , insoluble in water Easily oxidized in hot air 4FeO + O2 2 Fe 2O3 It react with dilute mineral acids producing iron ll salts and water FeO + 2HCL /dil FeCl2 +H2O FeO + H2SO4 /dil FeSO4 + H2O  2- Fe2O3 (iron lll oxide ) ferric oxide  Preparation BY adding alkali to aqueous solution of iron lll salt. (alkali like NH4OH , or KOH , NaOH ) The reaction will produce reddish brown ppt of iron lll hydroxide FeCL3 + 3NH4OH Fe(OH)3 +3NH4CL heating such ppt over 200°C produces the characteristic red color of iron lll oxide and water 1- by heating ferrous sulphate it produces Fe2O3 (iron lll oxide ) AND sulphur oxides 2FeSO4 Fe2O3 + SO3 + SO2 Here iron lll oxide is produced and not iron ll because the byproducts produced is oxidizing agent as SO3 which allow further oxidation to Fe2O3 AND thus some of them is reduced to SO2 Properties 1- occur as hematite in nature 2- blood red color 3- used in making red paints 4- react with CONC acids to produce iron lll salts Fe2O3 + 6HCL /CONC 2FeCL3 + H2O Fe2O3 + H2SO4 /CONC Fe2(SO4)3 + 3H2O  3-Fe3O4 (magnetic iron oxide)  It can be considered as a mixture of iron ll and lll oxides  Preparation 1- by action of hot air or steam on hot iron 3Fe + 2O2 Fe3O4 3Fe + 4H2O Fe3O4 +4H2 2- reduction of IRON lll 3Fe2O3 + CO 230-300° 2Fe3O4 +CO2 Properties 1- it is a strong magnet. 2-it react with conc acids to produce iron ll and iron lll salts (that proves it is a mixed oxide) Fe3O4 + 4 H2SO4 /CONC FeSO4 + Fe2(SO4)3 +4H2O 3- IT IS oxidized to iron lll when heated in air (so it losses its magnetic power by heating) FeCL3 FeCL3+ NaOH