Metals in the Periodic Table
- Mainly in Group I, Group II, and the Transition Block
- those near the staircase line
Properties1. High density, melting point and boiling point
2. Malleable and ductile
- due to close packing of the atoms in metals
- strong forces between these atoms
- high density except sodium
- high melting and boiling points except mercury and sodium
3. Thermal conductivity
- when a force is applied to a metal, the atoms can slide over one another
- malleable: can be bent and beaten into different shapes
- ductile: can be stretched to form wires
4. Electrical conductivity
- heat energy can be transferred from one atom to another by vibration as the atoms are very close together
- the outermost electrons also help to conduct heat
Metals always from positive ions
- when a metal is connected to a circuit, the free outermost electrons move towards the positive terminal
- to replace them, more electrons are fed into the metal from the negative terminal
Extremes in MetalsLightest: LithiumHeaviest: OsmiumMost brittle: Manganese and chromiumLowest melting point: MercuryHighest melting point: TungstenMost expensive: PlatinumRarest: RhodiumMost abundant: Aluminium
Metallic propertiesMetals have high:- density: high mass per unit volume- tensile strength: high strength of the metal under stress- durability: resistant to corrosion- malleability: ability to be made into sheets- ductility: ability to be made into wires- thermal conductivity: ability to conduct heat- electrical conductivity: ability to conduct electricity- sonority: ability to produce sound when struck
- a mixture of metallic elements or metallic with non-metallic.
- Pure metals are weak as the layers of atoms slide over each other easily. in alloy of 2 metals, they have different sizes of atoms so this distrupts the orderly layer of atoms making it difficult for atoms to slide over.
- Eg of alloys
- Steel: iron and carbon
- bronze: copper and tin
- brass: copper and zinc
- duralumin: aluminium, copper, magnesium
- Uses of duralumin: it is
light but strong and durable so used for aircraft parts, greenhouse
frames, overhead cables, curtain walling in high-rise buildings etc.
- pewter: tin and lead
- Uses of solder: mixture of tin and lead, has a much lower melting point than either of its components so more easily fusible --- suitable for welding electrical wire together
- Uses of stainless steel: is an alloy of iron containing chromium or nickel. Is the most expensive way
- applications for:
- medical instruments
- kitchen sinks
- steel objects in chemical factories and oil refineries
Reactivity series of metals
- Reactive metals tend to form positive ions easily, by losing electrons and forming compounds
- unreactive metals prefer to remain in uncombined form, as the element itself
- the order of reactivity is worked out from the metal's reaction (if any) with water or steam and acids
- if there is a reaction, the metal displaces hydrogen
- Metal + hydrogen ion ---> metal ion + hydrogen gas
| Metal||Metal with water/steam ||Metal with acid |
|react with cold water |
M(s) + 2H2O(l) --> MOH(aq) + H2(g)
Metal + Water --> Metal Hydroxide + Hydrogen
|violent reaction with dilute acids |
M(s) + 2HCl(aq) --> MCl2(aq) + H2(g)
Metal + Acid --> Metal Chloride + Hydrogen
|react with steam |
M(s) + 2H2O(g) --> MO(s) + H2(g)
Metal + Water --> Metal Oxide + Hydrogen
| react with dilute acids with decreasing ease|
M(s) + 2HCl(aq) --> MCl2(aq) + H2(g)
Metal + Acid --> Metal Chloride + Hydrogen
|do not react with water or steam || react with dilute acids with decreasing ease|
|do not react with water or steam || react only with concentrated acids|
- In the reactivity series, metals at the top, like potassium and sodium, react violently with cold water. Hence, they are stored under the surface of oil to prevent water vapour in the atmosphere from reacting with them
- eg. 2Na + 2H2O ---> 2NaOH + H2
- Down the series, the reactivity of the metal decreases.
- Magnesium will react only with steam, and for metals below iron there is no reaction with either cold water or steam.
- eg. Mg + H2O ---> MgO + H2
- With dilute hydrochloric acid, the metals at the top of the series react very violently. As we go down, the metals react less vigorously.
- Aluminium, although above iron and zinc, reacts more slowly because of a protective oxide coat on its surface.
- eg. Fe + 2HCl ---> FeCl2 + H2
- Below lead, there is no reaction with steam or with dilute acids and so hydrogen is never displaced. Hence its position in the series.
- The metals below hydrogen will react only with concentrated acids which are capable of oxidising the metal first to its oxide. Such acids are concentrated nitric or sulphuric acids
- eg. Cu + 4HNO3 ---> Cu(NO3)2 + 2NO2 +2H2O
Stability of metal compounds
- Compounds of metals high up in the reactivity series are stable and not easily decomposed by heating.
- Compounds of metals low down in the series are unstable, and are often decomposed by heating, or are easily reduced.
- The oxides of metals above zinc in the series can only be reduced to the metal by using electrolysis.
- At cathode, reduction occurs
- The oxides below can be reduced with reducing agents like carbon or hydrogen, except zinc oxide which cannot be reduced by action of hydrogen
- ZnO + C --> Zn + CO
- CuO + H2 --> Cu + H2O
| Metal||Oxide ||Hydroxide || Carbonate||Nitrate |
|electrolytic reduction ||stable to heat || stable to heat || decompose to nitrite and oxygen|
| electrolytic reduction || decompose to metal oxide and steam on heating|| decompose to metal oxide and carbon dioxide gas on heating|| decompose to metal oxide, nitrogen dioxide and oxygen on heating|
| reduced by heating with carbon|| decompose to metal oxide and steam on heating|| decompose to metal oxide and carbon dioxide gas on heating|| decompose to metal oxide, nitrogen dioxide and oxygen on heating|
| reduced by heating alone||unstable, do not exist || unstable, do not exist || decompose to metal, oxygen and nitrogen dioxide gas on heating|
- Down the series, reduction becomes easier because the metals prefer to exist as atoms, as opposed to ions
- For metal oxides like mercury(II) oxide, no reducing agent is needed - just heating alone
- Hydroxides of the metals calcium and below decompose to their corresponding oxide and give off steam, on heating. This can be confirmed by using anhydrous copper(II) sulphate which turns white to blue with steam
- Similarly, most carbonates, except sodium and potassium carbonates, undergo thermal decomposition again to a metal oxide, but this time giving off carbon dioxide gas. This can be confirmed by bubbling the gas through limewater, which turns milky with carbon dioxide
- Nitrates also decompose on heating, but the stable ones at the top of the series only decompose as far as the nitrite (nitrite(III)), giving off oxygen gas. This can be identified by the gas relighting a glowing splinter
- The majority of nitrates decompose to the metal oxide, giving off brown fumes of nitrogen dioxide as well as oxygen gas.
- 2Mg(NO3)2 ---> 2MgO + 4NO2 + O2
- The unstable nitrates at the bottom of the reactivity series decompose all the way to the metal itself
- 2AgNO3 ---> 2Ag + 2NO2 + O2
Displacement power of metalsDisplacement reaction is the displacement of ions of metal from compounds of metals lower in reactivity series by metals higher in reactivity series.
E.g. Magnesium displaces copper(II) chloride
Mg(s) + CuCl2(aq) -> MgCl2(aq) + Cu(s)
- For observation, we’ll see silver magnesium metal coated with brown copper metal
- Displacement is due to Mg atoms transfer electrons to Cu2+ ions forming Cu atoms.
Mg(s) → Mg2+
(aq) + 2e-
(aq) + 2e-
- Loss of electrons is due to it’s less reactive as less reactive metal has higher chance of losing electrons.
- That’s why when Mg is placed in KCl, no reaction occurs.
Mg(s) + KCl2
(aq) --> No reaction
Displacement of oxides
- The Thermit Reaction is an example of displacement of oxides.
- Iron(III) oxide and aluminium powder are heated in a crucible, with a magnesium fuse to start the reaction.
- The aluminium is more reactive, and takes the oxygen from the iron oxide, leaving molten iron at the bottom of the crucible.
- Fe2O3 + 2Al ---> Al2O3 + 2Fe
- This reaction is called the Thermit Reaction as it produces large quantities of heat.
- It has been used to weld railway lines in remote areas where normal welding techniques are not possible.
Displacement from solutions
- In general, the more reactive metal goes into solution displacing the less reactive.
- For eg, if iron filings were slowly added, with stirring, to a blue solution of copper(II) sulphate, the blue color would fade and become faintly greenish.
- This is because the copper has been pushed out, and is left as pink copper metal, while the iron has gone into solution as green iron(II) sulphate
- CuSO4 + Fe ---> FeSO
4 + Cu
- In displacement reactions, the powder form is used as powders have a greater surface area and so will react more quickly.
- Using ionic equations to show displacements:
Reaction of Metal Oxides with Carbon
- The lower the position of metal in reactivity series, the easier for carbon to remove oxygen from metal oxide by heating. At higher position, stronger heat is needed.
- E.g. CuO reacts with C can be reduced by bunsen burner flame temperature
- CuO(s) + C(s) --> Cu(s) + CO2(g)
- For iron oxide to be reduced, it needs very high temperature.
Reaction of Metal Oxides with Hydrogen
- The lower position of metal in reactivity series, the easier hydrogen remove oxygen from metal oxide by heating. At higher position, stronger heat is needed.
- E.g. PbO reacts with H2 can be reduced by bunsen burner flame temperature
- PbO(s) + H2(g) --> Pb(s) + H2O(l)
Decomposition of Metal Carbonates
- The lower position of metal in reactivity series, the easier hydrogen remove oxygen from metal oxide by heating. At higher position, stronger heat is needed.
- E.g. CuCO3 reacts decomposes by heat of bunsen burner flame temperature
- CuCO3(s) --> Cu(s) + CO2(g)
Extraction of MetalsMetals from Rocks
Extracting these metals
- Minerals – elements/compounds that make up rocks
- Metal ore – rock containing metal
Occurrence of Metals
- Metal ores are removed from ground.
- The ores contain useful and unwanted materials. Unwanted materials are separated to obtain concentrated mineral.
- Metal is extracted from the mineral.
- Metal ores are compounds, usually as:
- Metal oxides – metal + oxygen, eg: Al
- Metal sulphides – metal + sulphur, eg: HgS
- Metal carbonates – metal + carbon + oxygen, eg: MgCO3
- Least Reactive – easiest to extract; extracted by physical methods
- Less Rective – harder to extract than least reactive; by blast furnace; usually occur as compounds of oxides or sulphides.
- Most Reactive – hardest to extract – strong bonds in compounds; by electrolysis – decomposing compounds with electricity.
Uses of Metals
The choice of metals over another depends on 3 factors:
- Physical properties (e.g. melting point, strength, density, conductivity)
- Chemical properties (e.g. resists corrosion)
Advantages of recycling metals
- There are many iron on the surface but copper and tin are seriously reducing.
- High temperatures and pressures and greater depth increases hazards that prevent mining up to the lower part of crust, although there are more metals further down
- Ways to conserve metals
- Use alternative materials to replace the use of iron (e.g. use of plastic pipes instead of iron, use of glass bottles for soft drinks instead of aluminium)
- Recycle unused metals by melting them to produce new blocks of clean metal
- Recyling helps conserving metals, especially valuables such as gold and platinum.
- E.g. used computer parts processed to extract gold used for electrical contacts of processors and memory chips
- Recycling saves the cost of extracting new metals
- Recycling benefits environment, e.g. if there is a car wasteland, it causes eyesore
- Recycling metals can damage the environment by smelting process which sends a lot of fumes into the air
- Cost to separate metals from waste is high. E.g. separat metals in alloys is hard
- Transport costs for collecting scrap metal is high, e.g. trucks should be used
- People are not interested in depositing their used materials in recycling bins
- Iron is extracted from the iron ore haematite, Fe2O3
- Iron is extracted from the oxide in a blast furnace
- Iron made from blast furnace is not good as:
- it contains impurities which makes it brittle (can break easily)
- it cannot be bent or stretched
- Most iron is converted into steel which is an alloy of iron and carbon with small amounts of other elements. Advantages of steel:
- it is strong and tough
- it can be bent and stretched without shattering
Different Types of Steel:
- Impurities of iron is removed by blowing oxygen into molten iron to change the impurities into oxides. They are then combined with CaO and removed as slag.
- Carbon and other metals are added in certain amount to make steel.
- Mild steel – is a low carbon steel with 0.25% carbon
- It is strong and quite malleable. It is used for car bodies, ships, railway lines and steel rods to reinforce concrete
- Hard steel – is a high-carbon steel with about 1% carbon
- It is harder than mild steel and less malleable. It is used to make tools
- Stainless steel – is iron with large amounts of chromium and nickel
- It is hard, shiny and doesn’t rust. It is used to make cutleries, medical instrument and pipes in chemical industries.
Conditions for rustingTubes A B C
- Rusting – corrosion of iron and steel
- Rust – brown solid product formed during rusting
- Rust is hydrated iron(III) oxide Fe2O3.xH2O where water molecules varies.
- After a few days, only nail in tube A rust.
- This shows that air and water is needed for rust.
- In boiled water, the nail doesn’t rust in B as boiled water removes dissolved air while in C, CaCl keeps air dry so there’s no water.
- Surface protection: covers metal with a layer of substance
- Grease or oil (also help to lubricate)
- Metal Plating – covering metal with thin layer of another metal (e.g. tin, chromium, silver)
- Advantage – These methods are cheap (except metal plating)
- Disadvantage – If the layer is broken, air and water an reach metal to rust
- Sacrificial protection
- to sacrifice more reactive metal to corrode with water and air by layering it over less reactive metal (e.g. iron covered by magnesium).
- If layer is broken, water & air reach underneath layer, overlying metal still protect it.
- Galvanised Iron – is steel coated with zinc, usually used on roofs.
- Protecting ships – blocks of zinc are attached to hulls to corrode instead of steel which is the ship metal.
- Underground steel pipes – these are attached to magnesium block using insulated copper cables. Magnesium corrodes first than steel.
- Use of stainless steel
MCQ Questions1. Caesium is a metal that is more reactive than aluminium. Which reaction would produce caesium?a. electrolysing aqueous caesium chlorideb. electrolysing molten caesium chloridec. heating caesium carbonated. heating caesium oxide with carbon2. Which of the following processes does not result in the formation of both carbon dioxide and water?a. addition of a dilute acid to a carbonateb. burning ethanolc. burning methaned. heating crystals of hydrated sodium carbonate3. Which element is always present with iron in mild steel?a. aluminiumb. carbonc. chromiumd. nickel4. Hydrogen gas will reduce a. calcium oxideb. silver oxidec. magnesium oxided. potassium oxide5. Which oxide can be reduced to the metal using carbona. calcium oxideb. magnesium oxidec. sodium oxided. zinc oxide6. Which substance removes impurities from iron ore in the blast furnace?a. carbonb. limestonec. sandd. slag7. An excess of iron filings is added to a solution containing a mixture of the ions Mg2+, Ca2+, Cu2+ and Ag+. Which 2 metals will be displaced from this solution?a. calcium and copperb. calcium and magnesiumc. copper and silverd. magnesium and silver8. What reacts with hydrochloric acid to give hydrogen?a. ammoniab. ironc. silverd. sodium hydroxide9. Why does the color of aqueous potassium bromide change when chlorine gas is bubbled into it?a. a compound is formed between chlorine and bromineb. a solution of potassium chloride is formedc. the chlorine oxidises bromide ions to bromined. the potassium bromide is reduced10. Which carbonate decomposes on heating to give a black solid and a colourless gas?a. calcium carbonateb. copper(II) carbonatec. sodium carbonated. zinc carbonate11. Which substance is not an essential raw material in the extraction of iron in a blast furnace?a. airb. cokec. limestoned. sand12. Which element reacts with oxygen to form a compound that is a gas at room temperature?a. magnesiumb. hydrogenc. copperd. carbon13. Caesium is a metal that is more reactive than aluminium. Which reaction would produce caesium?a. electrolysing aqueous caesium chlorideb. electrolysing molten caesium chloridec. heating caesium carbonated. heating caesium oxide with carbon14. What is a disadvantage of recycling metals?a. collection and transportation costs moneyb. metal ores are a finite resourcec. most metals corrode slowly in the environmentd. scrap metal melts when heated15. Which of the following processes does not result in the formation of both carbon dioxide and water?a. addition of a dilute acid to a carbonateb. burning ethanolc. burning methaned. heating crystals of hydrated sodium carbonate16. Hydrogen gas will reducea. calcium oxideb. silver oxidec. magnesium oxided. potassium oxide17. Which element is always present with iron in mild steel?a. aluminiumb carbonc. chromiumd. nickel18. Which oxide can be reduced to the metal using carbon?a. calcium oxideb. magnesium oxidec. sodium oxided. zinc oxide19. Which substance removes impurities from iron ore in the blast furnace?a. carbonb. limestonec. sandd. slag20. What reacts with hydrochloric acid to give hydrogen?a. ammoniab. ironc. silverd. sodium hydroxide21. Which carbonate decomposes on heating to give a black solid and a colorless gas?a. calcium carbonateb. copper(II) carbonatec. sodium carbonated. zinc carbonate
22. Which substance is not an essential raw material in the extraction of iron in a blast furnace?a. airb. cokec. limestoned. sand23. Which element reacts with oxygen to form a compound that is a gas at room temperature?a. magnesiumb. hydrogenc. copperd. carbon24. A sample of air is slowly passed through aqueous sodium hydroxide and then over heated copper. Which gases are removed by this process?a. carbon dioxide and water vapourb. carbon dioxide and oxygenc. nitrogen and oxygend. nitrogen and water vapour25. When heated, solid X gives off a gas which turns limewater milky. The residue reacts with dilute acid and also with aqueous alkali. What is X?a. copper(II) carbonateb. magnesium carbonatec. sodium carbonated. zinc carbonate26. An element is burned in an excess of oxygen. Which statement about the oxide formed is always correct?a. it is a crystalline solidb. it is greater in mass than the elementc. it is soluble in waterd. it is white in color27. Which substance can be reduced by carbon?a. aluminium oxideb. calcium carbonatec. iron(III) oxided. magnesium oxide28. Which of the following is a typical property of transition metals?a. they form colored compoundsb. they have low densitiesc. they have low melting pointsd. they react with cold water to give hydrogen29. What happens when zinc is placed in aqueous copper(II) sulphate?a. copper atoms are oxidisedb. zinc atoms are oxidisedc. copper ions are oxidisedd. zinc ions are oxidised30. Which substance does not need air as a raw material for its manufacture?a. ammoniab. ironc. sodiumd. sulphuric acid31. Which of the following is not a use of silicon or its compounds?a. making fire-resistant plasticsb. making glassc. making polishesd. making smokeless fuel32. Compound X reacts with some metals to liberate hydrogen and is used to make fertilisers. It gives a white precipitate when added to aqueous barium nitrate. What is X?a. ammonium sulphateb. hydrochloric acidc. potassium nitrated. sulphuric acid33. Which industrial process uses iron as a catalyst?a. making ammonia from nitrogen and hydrogenb. making ethanol from ethene and steamc. making steeld. making sulphur trioxide from sulphur dioxide and oxygen34. Which pair of elements will combine to form an ionic compound?a. carbon and chlorineb. fluorine and sodiumc. hydrogen and oxygend. oxygen and carbon35. How does the mass of a sample of copper(II) oxide change when it is heated in hydrogen and in oxygen?
36. Sodium is a metal. Using only this information, what can be deduced about sodium?
| || mass after heating in hydrogen||mass after heating in oxygen |
| a|| decreases|| decreases|
| b|| decreases|| unchanged|
| c||unchanged || decreases|
| d|| unchanged|| unchanged|
a. it has a low melting point
b. it is a conductor of electricity
c. it is less dense than water
d. it is very reactive
37. Which substance reacts with water to form a soluble compound and an insoluble gas?
a. ammonium sulfate
c. calcium carbonate
38. Which compound does not give off a gas when heated?
a. hydrated copper(II) sulfate
b. hydrate sodium carbonate
c. magnesium carbonate
d. sodium carbonate
39. Which metal should be used in the sacrificial protection of the hull of a boat made from iron?
40. A coil of clean copper wire is suspended in a beaker of aqueous silver nitrate. Crystals of silver are deposited on the copper wire. Which statement is not correct?
a. the copper is oxidised
b. the solution turns blue
c. the total mass of the crystals of silver increases gradually
d. the total number of positive ions in the solution is unchanged
41. In the manufacture of iron by the blast furnace, which are the main gases that escape from the top of the blast furnace?
a. carbon monoxide, carbon dioxide, hydrogen
b. nitrogen, carbon dioxide, carbon monoxide
c. nitrogen, oxygen, steam
d. oxygen, carbon dioxide, sulfur dioxide
42. When heated, solid X gives off a gas. When this gas is bubbled through limewater, a white precipitate is formed. The residue after heating solid X reacts with dilute acid and also with aqueous alkali. What is X?
a. copper(II) carbonate
b. magnesium carbonate
c. sodium carbonate
d. zinc carbonate
43. The information below concerns 3 elements X, Y, and Z.
X: Its oxide is decomposed by heat to the element.
Y: Its carbonate is not decomposed by heat.
Z: Its oxide is not decomposed by heat but its carbonate decomposes.
In order of decreasing reactivity, the 3 elements should be arranged as:
a. Y Z X
b. X Y Z
c. Y X Z
d. X Z Y
Answers1. b2. d 3. b4. b5. d6. b7. c8. b9. c10. b11. d12. d13. b14. a15. d16. b17. b18. d19. b20. b21. b22. d23. d24. b25. d26. b27. c28. a29. b30. c (sodium is obtained through electrolysis)31. d32. d33. a34. b35. b
Structured Questions and Worked Solutions
1a. Under what conditions does water react with
In each case, name the products formed.
b. Water supplies are obtained from rivers, boreholes and reservoirs. The water must be treated before use. Describe and explain the two main processes in the purification of water supplies.
c. Water supplies that have passed through iron pipes contain iron(II) ions, Fe2+ and iron(III) ions, Fe3+.
In the presence of air, iron(II) ions are slowly changes to iron(III) ions.
Construct the equation for the reaction between iron(II) ions, hydrogen ions, H+, and oxygen to form iron(III) ions and water.
1ai. In cold water.
Products: sodium hydroxide and hydrogen
1aii. Heated with steam.
Products: magnesium oxide and hydrogen
1bi. filtration: solid particles are removed.
1bii. chlorination: germs and bacteria are killed by sterilising water with chlorine.
1c. 4Fe2+ (aq) + O2 (g) + 4H+ (aq) ---> 4Fe3+ (aq) + 2H2O (l)
2. Calcium oxide is produced by heating a mixture of limestone and coke in a lime kiln.
CaCO3 <---> CaO + CO2
ai. Explain the meaning of the symbol <--->
aii. In the lime kiln, the carbon dioxide is allowed to escape. Why does this increase the yield of calcium oxide?
b. The calcium oxide reacts with water to form slaked lime.
i. Give the equation for this reaction
ii. State a use of slaked lime
2ai. It shows that the decomposition of calcium oxide in the lime kiln is a reversible reaction.
2aii. The decrease in carbon dioxide concentration causes the equilibrium to shift to the right to produce more carbon dioxide to replace those that escaped. Therefore, more calcium carbonate decomposes to give calcium oxide.
2bi. CaO + H2O --> Ca(OH)2
2bii. It is used to treat acidic soils. It reacts with acid to produce salt and water.
3. Choose from the following metals to answer the questions below.
| aluminium||calcium ||copper ||iron |
|magnesium||potassium ||sodium ||zinc |
Each metal can be used once, more than once, or not at all.
Name a metal which
a. is manufactured by the electrolysis of its molten oxide
b. has a variable valency
c. is used to galvanise iron
d. has a carbonate which is coloured
e. is alloyed with zinc to make brass
4. In separate experiments, powdered samples of metal X and metal Y reacted with solutions of nickel(II) sulphate and of iron(II) sulphate. The following table shows how the colours of the solutions changed.
| || nickel(II) sulphate||iron(II) sukphate |
|metal X||Solution goes from green to colourless||Solution stays pale green|
|metal Y||Solution goes from green to colourless||Solution goes from pale green to colourless|
a. predict the order of reactivity for the four metals X, Y, nickel, and iron.
b. Metal Y was placed in aqueous copper(II) sulphate.
i. What colour change was seen?
ii. Give one other observation
c. Write the ionic equation, with state symbols, for the reaction between iron and aqueous nickel(II) sulphate.
a. from least reactive to most reactive: nickel, metal X, iron, metal Y
bi. blue copper(II) sulphate solution decolourises
bii. a reddish brown deposit is formed
c. Fe (s) + Ni2+ (aq) ----> Fe2+ (aq) + Ni (s)