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KS4 Chemistry. Transition Metals. Contents. Transition Metals. Introducing transition metals. Physical properties. Chemical properties. Uses. Summary activities. 3. 2. H. He. Li. Be. Ne. transition metals. Na. Mg. Al. Ar. K. Ca. Ga. Kr. Rb. Sr. In. Sn. Xe. Cs.
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KS4 Chemistry Transition Metals
Contents Transition Metals Introducing transition metals Physical properties Chemical properties Uses Summary activities
3 2 H He Li Be Ne transition metals Na Mg Al Ar K Ca Ga Kr Rb Sr In Sn Xe Cs Ba Tl Pb Bi Po Rn Br ? Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? Au ? ? ? La Hf Ta W Hg Y Te Ge I Zr Nb Mo Tc Ru Rh Pd Ag Cd Sb Re Sc At Ti V Cr Mn Fe Co Ni Zn Zn As Os Re Pt Ti V Cr Mn Rg ? Mt Rf O N C B Cu Ac Db Hs Sg Cl S P Bh Si F Ir Cd Sc Pd Se Cu Fe Ds Co La Ni Hf Ta W Ag Os Ir Pt Au Hg Y Zr Nb Mo Tc Ru Rh Fr Ra The transition metals Transition metals are located in the periodic table between group 2 and group 3. ‘Transition’ means ‘in-between’.
Common transition metals There are over 30 transition metals, but many are rare and have few uses. What are some of the most important and well-known transition metals? titanium chromium iron nickel copper silver platinum gold
Metal Ion Example of compound Transition metal ions All transition metals lose electrons when they react, and so form positive ions. Some transition metals only make one type of ion, for example: • silver only forms Ag+ ions; • zinc only forms Zn2+ ions. However, most transition metals can form more than one type of ion. They have variable valency. For example: Cu+copper (I) oxide – Cu2O copper Cu2+copper (II) oxide – CuO Fe2+iron (II) chloride – FeCl2 iron Fe3+iron (III) chloride – FeCl3
Contents Contents Transition Metals Introducing transition metals Physical properties Chemical properties Uses Summary activities
General properties The transition metals are often referred to as ‘typical’ metals because they have properties that most people associate with ‘common’ metals. Transition metals: • are hard, strong and have a high density; • are malleable and ductile; • are lustrous; • have high melting and boiling points (except mercury, which is liquid at room temperature); • are good conductors of heat and electricity.
Comparison with alkali metals How do the properties of transition metals compare with those of alkali metals? Transition metals: • are more dense – this means that, in a fixed volume of metal (e.g. 1cm3), there are more atoms of a transition metal than of an alkali metal; • have higher melting and boiling points – except mercury; • are harder and stronger – they are not brittle and cannot be cut with a knife.
Contents Transition Metals Introducing transition metals Physical properties Chemical properties Uses Summary activities
Sc Ti V Cr Mn Fe Co Ni Cu Zn decrease in reactivity Reactivity of transition metals Transition metals are less reactive than alkali metals.They tend to react relatively slowly, for example with airand water (except iron) and acid. The general trend is for reduced reactivity across periods. There are exceptions, such as zinc being more reactive than might be expected.
Rusting hydrated iron (III) oxide (rust) + + iron oxygen water + + 4Fe(s) 3O2(g) 2H2O(g) 2Fe2O3.H2O Rusting is an oxidation reaction between iron, oxygen and water. It is a type of corrosion. What are the word and chemical equations for the formation of rust?
Transition metals and colour How do transition metals compare to alkali metals?
Colour and transition metals Most transition metals form coloured compounds. For example: • iron (II) compounds are usually green e.g. iron (II) chloride (FeCl2) • iron (III) compounds are usually orange/brown e.g. iron (III) oxide (Fe2O3) – when hydrated this is rust • copper (II) compounds are blue e.g. copper (II) sulfate (CuSO4.H2O) – these can be turned white by heating the crystals to remove the water.
Uses of coloured compounds Coloured compounds of transition metals are used in many ways. For example: • stained glass windows • paints • glazes on pottery
iron (II) carbonate + iron oxide carbon dioxide heat + FeCO3(s) FeO(s) CO2(g) Thermal decomposition Compounds of transition metals can be broken down into simpler substances by heating them. This is called thermal decomposition. For example, carbonates of transition metals are broken down into metal oxides and carbon dioxide when heated. The reactants and products are different colours. How can the presence of carbon dioxide be tested?
Identifying transition metal ions The presence of transition metal ions in a solution can be tested by adding sodium hydroxide solution. If they are present, a metal hydroxide is formed. This is insoluble so it appears as a solid called a precipitate. Different metal ions produce different coloured precipitates. For example: • Fe2+ ions produce a grey/green precipitate of Fe(OH)2 • Fe3+ ions produce an orange/brown precipitate of Fe(OH)3 • Cu2+ ions produce a blue precipitate of Cu(OH)2
Contents Transition Metals Introducing transition metals Physical properties Chemical properties Uses Summary activities
Uses of iron Transition metals have many uses, and these are directly related to their physical properties. Iron is hard, strong, abundant and not too expensive. It is therefore used in construction and engineering, but it is usually turned into steel first.
Uses of titanium Titanium is as strong as steel but much lighter, and is very resistant to corrosion. Alloys of titanium are used in the aerospace industry, and in artificial joints, such as hip ball and sockets. Titanium dioxide is a brilliantly white compound used in paints, plastics, paper and toothpaste.
Uses of copper Copper is used in wires and cables because of its good electrical conductivity, and used in plumbing because it is unreactive with water. Copper is also used as a roofing material. The copper reacts slowly with gases and water in the air to create a thin green layer of copper compounds. This prevents the rest of the copper from reacting.
Alloys Transition metals are often mixed with other metals ornon-metals to form alloys. This changes the property of the metal so it is better suited for a particular purpose. • Steel is an alloy of iron and other elements, such as carbon, nickel, manganese and chromium. There are many different types of steel, each with different properties. • Brass is an alloy of 70% copper and 30% zinc. • Bronze is an alloy of 90% copper and 10% tin. • Cupronickel is an alloy of 75% copper and 25% nickel – it is used in ‘silver’ coins.
Catalysts Many transition metals and their compounds are used as catalysts. A catalyst is a substance that speeds up a chemical reaction without being used up. Catalysts are very important because they can save time, energy and money. • Nickel is a catalyst in the production of margarine (hydrogenation of vegetable oils). • Iron is a catalyst in the production of ammonia from nitrogen and hydrogen (the Haber process).
Catalysts – more examples What are other examples of transition metal catalysts? • Platinum is a catalyst in catalytic converters to reduce levels of polluting gases. It speeds up the conversion of carbon monoxide and nitrogen oxide to carbon dioxide and nitrogen. • Titanium is a catalyst in the production of plastics.
Contents Transition Metals Introducing transition metals Physical properties Chemical properties Uses Summary activities
Glossary (part 1) • alloy –A material containing two or more metals, or a metal and a non-metal. • catalyst – A substance that increases the speed of a chemical reaction without being used up. • corrosion – Damage to a metal caused by a chemical or electrochemical reaction such as rusting. • density –A measure of mass in a given volume. Often expressed in g/dm3. • ductile – Capable of being drawn out into a wire. • lustrous – Bright and shiny.
Glossary (part 2) • malleable – Capable of being bent and pressed into a different shape. • precipitate – A solid that forms in a solution by a physical or chemical reaction. • thermal decomposition – The process by which a substance is broken down into two or more products by heating it. • transition metal – An element located in the block between groups 2 and 3 of the periodic table. • valency– The number of electrons an atom must gain or lose to obtain a full outer shell.
