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Doc Brown's Chemistry  GCSE/IGCSE/O Level Chemistry Revision Notes

The Physical and Chemical Properties of the Transition Metal Elements Series

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Typical scandium, titanium, vanadium, chromium manganese, iron, cobalt, nickel, copper, zinc coloured solutions

 The physical properties of Transition Metals like density, melting points, boiling points, strength are described and discussed along with a description of the important transition metal chemical properties of e.g. titanium, vanadium, manganese, iron, cobalt, nickel, copper and zinc. There are also sections on how metals can be improved to increase their usefulness e.g. alloys and they are compared with the important 'non-transition' metals like aluminium, tin and lead.

PLEASE NOTE A Level students ! Advanced Level Chemistry Notes 3d block Transition Metals

and GCSE/IGCSE/O Level multiple choice QUIZ on Transition Metals

Some Reminders about the Periodic Table by way of an introduction

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The basic structure of the Periodic Table and where are the 'Transition Metals'?

  • The elements are laid out in order of Atomic Number
  • Hydrogen, 1, H, does not readily fit into any group
  • A Group is a vertical column of like elements e.g. Group 1 The Alkali Metals (Li, Na, K etc.), Group 7 The Halogens (F, Cl, Br, I etc.) and Group 0 The Noble Gases (He, Ne, Ar etc.). The group number equals the number of electrons in the outer shell (e.g. chlorine's electron arrangement is 2.8.7, the second element down in Group 7).
  • A Period is a complete horizontal row of elements with a variety of properties (more metallic to more non-metallic from left to right). All the elements use the same number of electron shells which equals the period number (e.g. sodium's electron arrangement 2.8.1, the first element in Period 3).
  • On Period 4 is a horizontal row of ten elements between Group 2 and Group 3, and from Sc to Zn are called the 1st Transition Metals Series of Elements ...
    • ... bottom-middle of the partial diagram of the Periodic Table above,
    • directly below them, but not shown, are further transition metal series,
    • so the Transition Metals Series are just a horizontal section of a period, ie a block of elements, in the middle of the Periodic Table.

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The Typical Physical Characteristics of Transition Metals

Z and symbol 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn
property\name scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc
melting pt./oC 1541 1668 1910 1857 1246 1538 1495 1455 1083 420
boiling pt./oC 2836 3287 3380 2672 1962 2861 2870 2730 2567 907
density/gcm-3 2.99 4.54 6.11 7.19 7.33 7.87 8.90 8.90 8.92 7.13

(a) Some General Physical Characteristics

  • Generally speaking they are hard, tough and strong (compared with the Group 1 Alkali metals!) because of the strong metallic atom-atom bonding.

  • Good conductors of heat and electricity (there have many free electrons per atom to carry thermal or electrical energy ).They are easily hammered and bent into shape. They are typically lustrous/shiny solids (or liquids).

(b) High Melting Point and Boiling Point

  • The bonding between the atoms in transition metals is very strong (see metallic bonding notes). The strong attractive force between the atoms is only weakened at high temperatures, hence the high melting points and boiling points (again compare with Group 1 Alkali Metals).
  • Mercury is in another transition metal, but unusually, it has a very low melting point of -39oC.
  • For example: iron melts at 1535C and boils at 2750C BUT a Group 1 Alkali Metal such as sodium melts at 98C and boils at 883C.

(c) High density

  • Another consequence of the strong bonding between the atoms in transition metals is that they are tightly held together to give a high density.
  • For example: iron has a density of 7.9 g/cm3 and sodium has a density of 0.97 g/cm3(and floats on water while fizzing! water has a density of 1.0 g/cm3).

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Their chemical properties and chemical reactions

(d)(i) Form coloured compounds and ions in solution

They tend to be much less reactive than the Alkali Metals. They do not react as quickly with water or oxygen so do not corrode as quickly. Transition metals tend to form more coloured compounds more than other elements either in solid form or dissolved in a solvent like water. Examples of the colours of some transition metal salts in aqueous solution are shown below (grey = colourless in the diagrams). These coloured ions/compounds often have quite a complex structure and indeed called complexes.

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  1. Sc - scandium salts, such as the chloride, ScCl3, are colourless and are not typical of transition metals
  2. Ti - titanium(III) chloride, TiCl3, is purple
  3. V - vanadium(III) chloride, VCl3, is green
  4. Cr - chromium(III) sulphate, Cr2(SO4)3, is dark green (chromate(VI) salts are yellow, dichromate(VI) salts are orange)
  5. Mn - manganese compound -  potassium manganate(VII), KMnO4, is purple (manganese(II) salts eg MnCl2 are pale pink)
  6. Fe - iron(III) chloride, FeCl3, is yellow-orange-brown.
    • Iron(II) compounds are usually light green and iron(III) compounds orange/brown.
  7. Co - cobalt sulphate, CoSO4, is pinkish
  8. Ni - nickel chloride, NiCl2, is green
  9. Cu - copper(II) sulphate, CuSO4, is blue.
    • Most common copper compounds are blue in their crystals or solution and sometimes green.
    • The blue aqueous copper ion, Cu2+(aq), actually has a more complicated structure:
      • *[Cu(H2O)6]2+(aq) and when excess ammonia solution is added,
      • after the initial gelatinous blue copper(II) hydroxide precipitate is formed, Cu(OH)2,
      • it dissolves to form the deep royal blue ion: *[Cu(H2O)2(NH3)4]2+(aq).
      • *are called complex ions and when coloured are typical of transition metal chemistry.
    • Copper(II) oxide, CuO, black insoluble solid, readily dissolving in acids to give soluble blue salts e.g.
      • copper(II) sulphate, CuSO4, from dilute sulphuric acid,
      • copper(II) nitrate, Cu(NO3)2, from dilute nitric acid
      • and greeny-blue copper(II) chloride, CuCl2, from dilute hydrochloric acid.
    • Copper(II) hydroxide, Cu(OH)2, blue gelatinous precipitate formed when alkali added to copper salt solutions.
    • Copper(II) carbonate, CuCO3, is turquoise-green insoluble solid, readily dissolving in acids, evolving carbon dioxide, to give soluble blue salts (see above)
    • Copper's valency or combining power is usually two e.g. compounds containing the Cu2+ ion.
      • However there are copper(I) compounds where the valency is one.
      • This variable valency, hence compounds of the same elements, but with different formulae, is typical of transition metal compounds e.g.
      • copper(I) oxide, Cu2O, an insoluble red-brown solid (CuO is black),
      • or copper(I) sulphate, Cu2SO4, a white solid.
  10. Zn - zinc salts such as zinc sulphate, ZnSO4, are usually colourless and are not typical of transition metals.

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(d)(ii) Some other odd bits of chemistry

  • See Acids, Bases and Salts page for the preparation of Transition Metal Salts from insoluble oxides, hydroxides or carbonates (insoluble bases).

  • Many of the transition metal carbonates are unstable on heating and readily undergo thermal decomposition.

    • metal carbonate ==> metal oxide + carbon dioxide

    • e.g.

    • copper(II) carbonate ==> copper(II) oxide + carbon dioxide

      • CuCO3(s) ==> CuO(s) + CO2(g)

    • or

    • zinc carbonate ==> zinc oxide + carbon dioxide

      • ZnCO3(s) ==> ZnO(s) + CO2(g)

    • In general the equation is ...

    • MCO3(s) ==> MO(s) + CO2(g) where M could be Fe, Cu, Mn or Zn

    • The carbon dioxide can be confirmed by giving a white milky precipitate with limewater.

    • Sometimes the two solids show a colour change eg

      • for M = Cu: turquoise green carbonate ==> black copper(II) oxide

      • for M = Zn: white carbonate ==> white zinc oxide, but yellow hot

  • Many transition metal ions (e.g. in soluble salt solutions) give hydroxide precipitates when mixed with aqueous sodium hydroxide solution.

    • These reactions can be used to help identify transition metal ions in solution

  • transition metal salt solution + sodium hydroxide ==> solid hydroxide precipitate + sodium salt

  • ionically the precipitation reaction is :

    • metal ion + hydroxide ion ==> hydroxide precipitate

    • M2+(aq) + 2OH-(aq) ==> M(OH)2(s) 

      • M can be for the ...

        • iron(II) ion Fe2+, pale green in aqueous solution,

        • which gives a dark grey-green gelatinous precipitate of iron(II) hydroxide with sodium hydroxide solution

        • ,
        • e.g.

        • iron(II) sulfate + sodium hydroxide ==> iron(II) hydroxide + sodium sulfate

          • FeSO4(aq) + 2NaOH(aq) ==> Fe(OH)2(s) + Na2SO4(aq)

        • or

        • iron(II) chloride + sodium hydroxide ==> iron(II) hydroxide + sodium chloride

          • FeCl2(aq) + 2NaOH(aq) ==> Fe(OH)2(s) + 2NaCl(aq)

        • For these reactions the ionic equation is ..

          • Fe2+(aq) + 2OH-(aq) ==> Fe(OH)2(s)

      • or for the copper(II) ion Cu2+, blue in aqueous solution,

        • which gives a blue copper(II) hydroxide precipitate with sodium hydroxide solution.

        • e.g.

        • copper(II) sulphate + sodium hydroxide ==> copper(II) hydroxide + sodium sulphate

          • CuSO4(aq) + 2NaOH(aq) ==> Cu(OH)2(s) + Na2SO4(aq)

        • or

        • copper(II) chloride + sodium hydroxide ==> copper(II) hydroxide + sodium chloride

          • CuCl2(aq) + 2NaOH(aq) ==> Cu(OH)2(s) + 2NaCl(aq)

        • For these reactions the ionic equation is ..

          • Cu2+(aq) + 2OH-(aq) ==> Cu(OH)2(s)

        • Note that the copper ion can be also detected by its flame colour of green-blue.

          • The flame test is conducted by dipping a nichrome (cheap)/platinum (expensive) wire into a copper salt solution and placing the end of the wire plus drop into the hottest part of a roaring bunsen flame when you see flashes of blue and green colour.

    • and for the iron(III) ion Fe3+:

      • giving a brown iron(III) hydroxide precipitate with sodium hydroxide solution,

      • e.g.

      • iron(III) chloride + sodium hydroxide ==> iron(III) hydroxide + sodium chloride

        • FeCl3(aq) + 3NaOH(aq) ==> Fe(OH)3(s) + 3NaCl(aq)

      • the ionic equation is ...

        • Fe3+(aq) + 3OH-(aq) ==> Fe(OH)3(s)

    • These hydroxide precipitates are basically solids, but of a somewhat gelatinous nature because they incorporate lots of  water in their structure.

  • Also note that iron has two valencies or combining power giving different compound formulae. Multiple valency, hence multiple compound formation, is another characteristic (but not unique) feature of transition metal chemistry.

    • The valency of chlorine is 1 and iron can have a combining power of 2 (II) or 3 (III).

    • FeCl2 iron(II) chloride (once called ferrous chloride)

    • FeCl3 iron(III) chloride (once called ferric chloride)

      • The number in Roman numerals is the valency or combining power e.g.

      • oxygen's valency is 2 and copper, another transition element, has a valency of 1 (I) or 2 (II)

      • so we have Cu2O copper(I) oxide (once called cuprous oxide)

        • and CuO copper(II) oxide (once called cupric oxide).

          • hence the need for the valency of the metal of the metal to be shown in Roman numerals.

  • There are more details and more tests on the Chemical Identification page (use the alphabetical list at the top).

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(e) Catalytic Properties - Uses of Transition Metals

(1) The metallic elements themselves are used as catalysts

  • Many transition metals are used directly as catalysts in industrial chemical processes and in the anti-pollution catalytic converters in car exhausts.
  • For example iron is used in the HABER PROCESS for the synthesis of ammonia:
    • Nitrogen + Hydrogen ==> Ammonia (via a catalyst of Fe atoms)
    • or N2(g) + 3H2(g) ==> 2NH3(g) 
  • Platinum and rhodium (in other transition series below Sc-Zn) are used in the catalytic converters in car exhausts to reduce the emission of carbon monoxide and nitrogen monoxide, which are converted to the non-polluting gases nitrogen and carbon dioxide.
  • 2NO(g) + 2CO(g) ==> N2(g) + 2CO2(g)
  • Nickel is the catalyst for 'hydrogenation' in the margarine industry. It catalyses the addition of hydrogen to an alkene carbon=carbon double bond (>C=C< + H2 ==> >CH-CH<). This process converts unsaturated vegetable oils into higher melting saturated fats which are more 'spreadable' with a knife!

(2) Some compounds of transition metals are also used as catalysts

  • As well as the metals, the compounds of transition metals also acts as catalysts.
    • For example manganese dioxide (or manganese(IV) oxide), MnO2, a black powder, readily decomposes an aqueous solution of hydrogen peroxide:
      • Hydrogen peroxide ==> water + oxygen
        • 2H2O2(aq) ==> 2H2O(l) + O2(g)
      • A useful reaction in the laboratory for preparing oxygen gas.
    • Vanadium(V) oxide (vanadium pentoxide, V2O5) is used as the catalyst in converting sulphur dioxide into sulphur trioxide as a stage in the manufacture of sulphuric acid in the CONTACT PROCESS.
      • 2SO2(g) + O2(g) ==> 2SO3(g) (via V2O5 catalyst)
      • A very important industrial process because sulphuric acid is a widely used chemical in industry.

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(f) More on the Uses of Transition Metals and their compounds

  • Transition metals are good conductors of heat and electricity and can be bent or hammered into shape (malleable), readily drawn into wire (ductile), quite strong physically - made stronger when alloyed with other materials.

  • This makes transition metals are useful as structural materials and for making things that must allow heat or electricity to pass through them easily and useful construction materials.

  • Pure copper, gold, iron (transition metals) and lead and aluminium (non-transition metals) are too soft for many uses and so are mixed with small amounts of similar metals to make them harder for everyday use.
  • Transition metals are extremely useful metals on account of their physical or chemical properties eg lack of corrosion and greater strength compared to the Group 1 Alkali Metals.
  • Many are used in alloys, with a wide range of applications and uses.
    • An ALLOY is mixture of metal with at least one other metallic or non-metallic substances - usually other elements.
    • By mixing metal with metal (and sometimes non-metals) together to make alloys you can improve the metal's properties to better suit a particular purpose.
    • Quite often the presence of different atoms stops the layers of the metal sliding over each other when stressed so making the metal tougher (see Metal Structure for more details).
    • The main point about using alloys is that you can make up, and try out, all sorts of different compositions until you find the one that best suits the required purpose in terms of tensile/compression strength, malleability, electrical conductivity or corrosion resistance etc.
  • For catalysts - see above. Their strength and hardness makes them very useful as structural materials.
(c) doc bIRON, Fe
  • Iron is a good conductor of heat and can be bent or hammered into shape (malleable), quite strong physically - made stronger when alloyed with other materials.

  • This makes iron useful as structural material and for making things that must allow heat to pass through easily and useful construction materials.

  • Why make the alloy steel?
    • Most metals in everyday use are alloys.

    • Steel is an alloy because it is a mixture of a metal (iron) with other elements (carbon and perhaps other metals too).

    • Iron from the blast furnace contains about ~96% iron with ~4% of impurities including carbon, silica and phosphorus.

    • In this state the cast iron is too hard and too brittle for most purposes.

    • Cast iron is hard and can be used directly for some purposes eg manhole covers, railings because of its strength in compression and is hard wearing.

    • However, if all the impurities are removed, the resulting very pure iron is too soft for any useful purpose.

    • Therefore, strong useful steel is made by controlling the amount of carbon and selected metals to produce an alloy mixture with the right physical properties fit for a particular application e.g. steel for car bodies, chrome stainless steel, extremely hard and tough tungsten-iron steel alloys etc.

    • The real importance of alloys is that they can be designed to have properties for specific uses.

    • eg low-carbon steels are easily shaped for car bodies, high-carbon steels are hard, and stainless steels are resistant to corrosion etc.

  • When alloyed with 0.1 to 1% carbon iron forms mild steel which is not brittle, but is more malleable and corrosion resistant than cast iron. Mild steel is used for food cans, car bodies (but galvanising and several coats of paint help it to last!) and machinery etc.
  • Steel is an alloy based on iron mixed with carbon and usually other metals added too. There are huge number of steel 'recipes' which can be made to suit particular purposes by changing the % carbon and adding other metals e.g. titanium steel for armour plating.
    • Low-carbon steels (0.1 to 1.0% carbon) are easily shaped for car bodies

    • High-carbon steels (1.5% carbon, often with other metals too) are hard wearing and inflexible and can be used for cutting tools, bridge construction.

    • Stainless steels have chromium (and maybe nickel) added and are much resistant to corrosion (from oxygen/water) than iron or plain steel which readily rust. Objects made of iron or plain steel, particularly those exposed to the weather, regularly have to be painted or coated with some other protective layer from the effects of water and oxygen.

  • Remember! If iron or steel becomes badly corroded, there is no strength in rust!, and, the thicker the rust layer, the thinner and weaker the supporting iron or steel layer, hence the possibility of structural failure.

    • Therefore, most iron and steel structures exposed to the outside weather are maintained with a good coating of paint which may be regularly replaced.

    • See notes on Corrosion of Metals and Rust Prevention

    • Chromium steel (stainless steel, mixing and melting together Fe + Cr and maybe Ni too) with good anti-corrosion properties, used for cutlery and chemical plant reactors.
(c) doc btop sub-indexCOPPER, Cu
  • Copper has properties that make it useful for electrical wiring and plumbing.
    • Copper is a good conductor of electricity and heat, can be bent but is hard enough to be used to make pipes or tanks and does not react with water.
  • The alloy BRASS is a mixture copper and zinc. It is a much more hard wearing metal than copper (too soft) and zinc (too brittle) but is more malleable than bronze for 'stamping' or 'cutting' it into shape.
  • Copper is used in electrical wiring because it is a good conductor of electricity but for safety it is insulated by using poorly electrical conductors like PVC plastic.
  • Copper is used in domestic hot water pipes because it is relatively unreactive to water and therefore doesn't corrode easily.
  • Copper is used for cooking pans because it is relatively unreactive to water and therefore doesn't corrode easily, readily beaten or pressed into shape but strong enough, it is high melting and a good conductor of heat.
  • Copper is also used as a roof covering and weathers to a green colour as a surface coating of a basic carbonate is formed on corrosion.
  • The alloy BRONZE is a mixture of copper and tin (Sn) and is stronger than copper or tin (both easily bent metals) and just as corrosion resistant, e.g. used for sculptures.
  • The alloy cupronickel is made by mixing copper and nickel and is a hard wearing metal used in 'silver' coinage.
  • Iron and steel are used for boilers because of their good heat conduction properties and high melting point.
  • Copper compounds are used in fungicides and pesticides e.g. a traditional recipe is copper sulphate solution plus lime is used to kill greenfly.
  • Copper is alloyed with nickel to give 'cupro-nickel', an attractive hard wearing 'silvery' metal for coins.
  • Steel, iron or copper are used for cooking pans because they are malleable, good heat conductors and high melting.
  • NICKEL is alloyed with copper to give 'cupro-nickel', an attractive hard wearing 'silvery' metal for coins.
(c) doc bZINC
  • Zinc is used to galvanise (coat) iron or steel to sacrificially protect them from corrosion. The zinc layer can be put on the iron/steel object by chemical (see electroplating and below) or physically dipping it into a bath of molten zinc.
  • Zinc sulphate solution can be used as the electrolyte for electroplating/galvanising objects with a zinc layer.
  • Zinc is used as a sacrificed electrode in a zinc-carbon battery. It slowly reacts with a weakly acidic ammonium chloride paste, converting chemical energy into electrical energy.
  • The alloy BRASS is a mixture copper and zinc. It is a much more hard wearing metal than copper (too soft) and zinc (too brittle) but is more malleable than bronze for 'stamping' or 'cutting' it into shape.
  • Gold is also a transition metal and gold alloys are used in jewellery because pure gold is too soft. Metals like copper, nickel, palladium and silver are used to 'harden' gold.
(c) doc bTransition metal compounds (often oxides) of copper, iron, chromium and cobalt are used to pigments for artwork, and give bright colours to stained glass and ceramic/pottery glazes e.g.
  • Paint pigments: chromium oxide Cr2O3 green, iron oxide (haematite) Fe2O3 red-brown, manganese oxide MnO2 black, copper hydroxide-carbonates (malachite-green, azurite-blue) and titanium dioxide TiO2 white.
  • Stained glass: cobalt oxide CoO blue, iron oxide/carbonate green, Cu metal red, CuO turquoise.
  • NICHROME is an alloy of chromium and nickel. It has a high melting point and a high electrical resistance and so it is used for electrical heating element wires.
  • NITINIOL: Titanium and nickel are the main components of Nitinol 'smart' alloys which are very useful intermetallic compounds. Nitinol belongs to a group of shape memory alloys (SMA) which can 'remember their original shape'. For example they can regain there original shape on heating (e.g. used in thermostats in cookers , coffer makers etc.) or after release of a physical stress (e.g. used in 'bendable' eyeglass frames, very handy if you tread on them!). The other main metal used in these
  • Titanium is a strong metal that has a low density and a high resistance to corrosion which makes a good structural material.
    • Titanium alloys are amongst the strongest lightest of metal alloys and used in aircraft production.

    • As well as its use in aeroplanes it is an important component in nuclear reactor alloys and for replacement hip joints because of its light and strong nature AND doesn't corrode easily.

    • It is one of the main components of Nitinol 'smart' alloys. Nitinol belongs to a group of shape memory alloys (SMA) which can 'remember their original shape'. For example they can regain there original shape on heating (e.g. used in thermostats in cookers , coffer makers etc.) or after release of a physical stress (e.g. used in 'bendable' eyeglass frames, very handy if you tread on them!). The other main metal used in these very useful intermetallic compounds is nickel.

      • Nitinol is an acronym for 'Nickel Titanium Naval Ordinance Laboratory' betraying, like so many technological developments, its military origins, but now acquiring many 'peaceful' uses.

  • TUNGSTEN is used as the filament in light bulbs because its melting point is so high.
  • Transition metals like platinum and rhodium are used as metal catalysts in the catalytic converters used in car vehicle exhausts to reduce carbon monoxide and nitrogen oxide polluting emissions.
  • Bright, shiny and relatively unreactive copper, silver and gold are used in jewellery.
  • There is a note about the bonding in metals and structure of alloys on another page.
  • Metals can become weakened when repeatedly stressed and strained leading to changes in the crystal structure of the metal and it becomes more brittle. These faults developing in the metal structure is called 'metal fatigue' or 'stress fractures'. If the metal fatigue is significant it can lead to the collapse of a metal structure. So it is important develop alloys which are well designed, well tested and will last the expected lifetime of the structure whether it be part of an aircraft (eg titanium aircraft frame) or a part of a bridge (eg steel suspension cables).

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(g) What about the uses of non-transition metals?

Note on Aluminium

  • Aluminium is NOT a transition metal !
    • e.g. it does not form coloured compounds, it does not act as a catalyst etc.
    • BUT it is high melting, of low density and one of the most used and useful non-transition metals.
    • It is rather weak BUT when alloyed with copper, manganese and magnesium and  it forms a much stronger alloy called duralumin.
    • It does not readily corrode due to a permanent Al2O3 aluminium oxide layer on the surface which does not flake off and protects the aluminium from further oxidation.
    • Because of its alloyed strength, lightness and anti-corrosion properties it is used in aircraft construction, window frames, hifi chassis etc.
    • Its a good conductor of heat and can be used in radiators.
    • Its quite a good conductor of electricity, and also because its light, it is used in conjunction with copper (excellent electrical conductor) in overhead power lines (don't want them too heavy when iced up!).
      • The cables however do have a steel core for strength!
      • Poorly electrical conducting ceramic materials are used to insulate the wires from the pylons and the ground.

Other non-transition metals and their uses

  • A mixture of molten tin and lead (neither are transition metals) produces the solid alloy SOLDER which is a relatively low melting solid for electrical connections.

  • Tin is an unreactive metal, doesn't react with water, and is used to coat more corrodible metals like iron-steel. A 'tin can' is actually made of steel with a fine protective coating of tin metal over the surface of it.

  • Lead is a soft, very malleable relatively unreactive metal used in roofing.

    • 'Flashings' are used to seal sections of roofs e.g. between walls and the ends of layers of tiles or slates because it doesn't react with water and is very malleable..

    • It is used with lead oxide in the manufacture of electrodes of road vehicle car batteries.

    • Because of its high density it is used as a shield from dangerous alpha/beta/gamma radiation from radioactive materials and X-rays, so it is used in nuclear processing facilities etc. and radiographers wear a lead apron when you go for an X-ray on your bones.

  • PEWTER is an alloy of mainly tin plus small amounts of copper, bismuth (Bi) and antimony (Sb), it is stronger than tin but is easy to etch and engrave.

  • DENTAL AMALGAM ALLOY is a mixture of tin, mercury and silver (a transition metal). When first prepared its soft and malleable before hardening to that undesired filling! It has good anti-corrosion properties and resists the attack of acidic products produced by bacteria in the mouth. An amalgam is an alloy metal compound made from a mixture of mercury and other metals which may be liquid and set to a solid after preparation.

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More on iron and examples of how metals can be made more useful

 Iron can be made more useful by mixing it with other substances to make various types of steel. Many metals can be given a coating of a different metal to protect them or to improve their appearance.

  • The properties of iron can be altered by adding small quantities of other metals or carbon to make steel.

  • Steels are alloys since they are mixtures of iron with other metals or with non-metals like carbon or silicon.

  • Making Steel:

    • (1) Molten iron from the blast furnace iron extraction process is mixed with recycled scrap iron

    • (2) Then pure oxygen is passed into the mixture and the non-metal impurities such as silicon or phosphorus are then converted into acidic oxides (oxidation process) ..

      • e.g. Si + O2 ==> SiO2, or 4P + 5O2 ==> P4O10

    • (3) Calcium carbonate (a base) is then added to remove the acidic oxide impurities (in an acid-base reaction). The salts produced by this reaction form a slag which can be tapped off separately.

      • e.g. CaCO3 + SiO2 ==> CaSiO3 + CO2 (calcium silicate slag)

    • Reactions (1)-(3) produce pure iron.

    • Calculated quantities of carbon and/or other metallic elements such as titanium, manganese or chromium are then added to make a wide range of steels with particular properties for specific purposes i.e. match the properties of the steel alloy to its use.

    • Because of the high temperatures the mixture is stirred by bubbling in unreactive argon gas!

    • Economics of recycling scrap steel or ion: Most steel consists of >25% recycled iron/steel and you do have the 'scrap' collection costs and problems with varying steel composition* BUT you save enormously because there is no mining cost or overseas transport costs AND less junk lying around! (NOTE: * some companies send their own scrap to be mixed with the next batch of 'specialised' steel they order, this saves both companies money!)

  • top sub-indexDifferent steels for different uses:

    • High % carbon steel is strong but brittle.

    • Low carbon steel or mild steel is softer and is easily shaped and pressed e.g. into a motor car body.

    • Stainless steel alloys contain chromium and nickel and are tougher and more resistant to corrosion.

    • Very strong steels can be made by alloying the iron with titanium or manganese metal.

  • There is a note about the bonding and structure of alloys on another page.

  • However, apart from expensive stainless steels using chromium and nickel mixed with iron, most steel alloys readily rusting leading to potential structural weakness and failure or the extra costs involved in protecting the steel.

  • Steel can be galvanised by coating in zinc, this is physically done by dipping the object into a bath of molten zinc. On removal and cooling a thin layer of zinc is left on. The zinc chemically bonds to the iron via the free electrons of both metals - its all the same atoms to them! It can also be done by electroplating (details below).

  • Steel (and most metals) can be electroplated.

    • The steel object to be plated is made the negative electrode (cathode) and placed in a solution containing ions of the plating metal.

    • The positive electrode (anode) is made of the pure plating metal (which dissolves and forms the fresh deposit on the negative electrode).

    • Nickel, zinc, copper, silver and gold are examples of plating metals.

    • The details of copper purification amount to copper plating, so all you have to do is swap the pure negative copper cathode with the metal you want to coat (e.g. Ni, Ag or Au or any material with a conducting surface). Swap the impure positive copper anode with a pure block of the metal you want to form the coating layer. The electrodes dip into a salt solution of nickel, zinc, copper, silver or gold ions etc. and a low d.c. voltage passed through. If M = Ni, Cu, Zn ....

      • At the positive (+) anode, the process is an oxidation, electron loss, as the metal atoms dissolve to form metal(II) ions.

      • M(s) ==> M2+(aq) + 2e-

      • at the negative (-) cathode, the process is a reduction, two electron gain by the attracted metal(II) ions to form neutral metal atoms on the surface of the metal being coated.

      • M2+(aq) + 2e- ==> M(s)

      • For silver plating it is Ag+, Ag and a single electron change.

      • Any conducting (usually metal) object can be electroplated with copper or silver for aesthetic reasons or steel with zinc or chromium as anti-corrosion protective layer.

  • Many other metals have countless uses e.g. zinc

    • Zinc is used to make the outer casing of zinc-carbon-weak acid batteries.

    • Zinc is alloyed with copper to make the useful metal brass (electrical plug pins). Brass alloy is stronger and more hardwearing than copper AND not as brittle as zinc.

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Another transition metal - Titanium - How is it produced? What is it used for?

Titanium is a very important metal for various specialised uses. It is more difficult  to extract from its ore than other, more common metals.

  • Titanium is a transition metal and is strong and resistant to corrosion.

    • Titanium alloys are amongst the strongest and lightest of metal alloys.

    • There is a note about the bonding and structure of alloys on another page.

    • It is used in aeroplanes, in nuclear reactor alloys and for replacement hip joints.

    • It is one of the main components of Nitinol 'smart' alloys. Nitinol belongs to a group of shape memory alloys (SMA) which can 'remember their original shape'. For example they can regain there original shape on heating (e.g. used in thermostats in cookers , coffer makers etc.) or after release of a physical stress (e.g. used in 'bendable' eyeglass frames, very handy if you tread on them!). The other main metal used in these very useful intermetallic compounds is nickel.

      • Nitinol is an acronym for 'Nickel Titanium Naval Ordinance Laboratory' betraying, like so many technological developments, its military origins, but now acquiring many 'peaceful' uses.

  • Titanium is extracted from the raw material is the ore rutile which contains titanium dioxide.

  • The rutile titanium oxide ore is heated with carbon and chlorine to make titanium chloride

    • TiO2 + 2Cl2 + C ==> TiCl4 + CO2

  • After the oxide is converted into titanium chloride TiCl4, it is then reacted with sodium or magnesium to form titanium metal and sodium chloride or magnesium chloride. This is an expensive process because sodium or magnesium are manufactured by the costly process of  electrolysis (electricity is the most costly form of energy).

    • This reaction is carried out in an atmosphere of inert argon gas so none of the metals involved becomes oxidised by atmospheric oxygen.

    • TiCl4 + 2Mg ==> Ti + 2MgCl2 or TiCl4 + 4Na ==> Ti + 4NaCl

    • These are examples of metal displacement reactions e.g. the less reactive titanium is displaced by the more reactive sodium or magnesium.

    • Overall the titanium oxide ore is reduced to titanium metal (overall O loss, oxide => metal)

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PLEASE NOTE A Level students ! Advanced Level Chemistry Notes 3d block Transition Metals

Revision KS4 Science IGCSE/O level/GCSE Chemistry Information Study Notes for revising for AQA GCSE Science, Edexcel GCSE Science/IGCSE Chemistry & OCR 21st Century Science, OCR Gateway Science, CCEA/CEA GCSE science-chemistry, WJEC GCSE science-chemistry (revise courses equal to US grades 8, 9, 10)

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