(a)-(c) Physical properties * (d) Chemical-reactions properties * (e) Use as catalysts * (f) More on uses of Transition Metals/compounds/alloys * (g) Note on uses of other non-transition metals/alloys e.g. aluminium/duralumin (Al is not a transition metal)

LINKS to other related pages relating to metals: Extra Industrial Chemistry * Metal Extraction * Metal Reactivity * Periodic Table * steel making and alloy uses and other metal uses * Transition Metal m/c QUIZ * multi-word fill quiz * GCSE notes on Group 1 Alkali Metals * detailed AS-A2 Advanced Level Notes on s-block Gps 1-2 Metals * EMAIL query?comment

Some Reminders about the Periodic Table

• 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 8 or 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 first Transition Metals Series of Elements
• A summary of some TRANSITION METAL DATA e.g. melting/boiling points, densities and more advanced data, is on another webpage and is suitable for GCSE, AS, A2 and US grades 9-12 courses.

(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 (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 -39^oC.
For example: iron melts at 1535°C and boils at 2750°C BUT a Group 1 Alkali Metal such as sodium melts at 98°C and boils at 883°C.

(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).

(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. The colours of some transition metal salts in aqueous solution are shown below.

1. Sc - scandium salts, such as the chloride, ScCl_3, 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,
     • 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.

• 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

  • or zinc carbonate ==> zinc oxide + carbon dioxide

  • MCO_3(s) ==> MO_(s) + CO_2(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.

• 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

    ,

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

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

  • and the iron(III) ion Fe³⁺: Fe³⁺_(aq) + 3OH^-_(aq) ==> Fe(OH)_3(s)

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

  • These precipitates are basically solids, but of a somewhat gelatinous nature because they incorporate 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.

• 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 Synthesis of ammonia:
  • Nitrogen + Hydrogen ==> Ammonia (via a catalyst of Fe atoms)
  • or N_2(g) + 3H_2(g) ==> 2NH_3(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) ==> N_2(g) + 2CO_2(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.
• EXAMPLES
  • For example manganese dioxide (or manganese(IV) oxide), MnO₂, a black powder, readily decomposes an aqueous solution of hydrogen peroxide:
    • Hydrogen peroxide ==> water + oxygen
    • or 2H₂O_2(aq) ==> 2H₂O_(l) + O_2(g)
    • A useful reaction in the laboratory for preparing oxygen gas.
  • Vanadium pentoxide is used as the catalyst in converting sulphur dioxide into sulphur trioxide as a stage in the manufacture of sulphuric acid.
    • 2SO_2(g) + O_2(g) ==> 2SO_3(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 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 (a mixture of metal with at least one other metallic or non-metallic substance). For catalysts - see above. Their strength and hardness makes them very useful as structural materials.

IRON, Fe

• Cast iron is used for man-hole covers because it is so hard wearing but it is brittle due to a high carbon content.
• When alloyed with 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.

• CHROMIUM, Cr
  • 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.

COPPER, Cu

• 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 and just as corrosion resistant, e.g. used for sculptures.
• 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.

ZINC

• 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.

Transition 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
• 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.

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

Note on Aluminium

• It 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 metals and their uses

• A mixture of tin and lead is mixed to give the alloy SOLDER which is a relatively low melting solid for electrical connections.

• Tin is an unreactive metal 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. Electrical cables can be encased in it. 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. 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.

Links to other information of uses of metals: Extra Industrial Chemistry and sodium in Group 1 alkali Metals.

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