Physical properties of metals and non-metals
A copper wire carries current and can be bent; a lump of coal is dull and crumbles when hit.
Metals are usually lustrous, hard, malleable (beaten into sheets), ductile (drawn into wires), sonorous and good conductors of heat and electricity. Non-metals are usually dull, brittle, non-sonorous and poor conductors.
Equation / formula : Exceptions: mercury is a liquid metal; sodium and potassium are soft and cut with a knife; gallium melts in the hand. Graphite (a non-metal) conducts electricity; diamond is the hardest natural substance; iodine is lustrous.
In the figure : Remember the exceptions: graphite and mercury.
Rule 1 : Using a property to choose a material — Match the use to the property.
- Easy : Electric wires: copper (ductile, conductor).
- Medium : Cooking pans: copper/aluminium (good heat conductors) with plastic handles (poor conductors).
- For exams : Silver foil on sweets is thin because silver is highly malleable; bells are made of metal because they are sonorous.
Rule 2 : Comparing a metal and a non-metal — Look at lustre, hardness, melting point, density and conduction together.
- Easy : Iron: shiny, conducts. Sulphur: yellow, brittle, does not conduct.
- Medium : Metals generally have high melting points; non-metals low (iodine sublimes).
- For exams : Exceptions: Na and K melt at low temperature; carbon (diamond) has a very high melting point.
Metals are good conductors because they have free electrons that carry heat and charge.
Saying all non-metals are insulators. Graphite conducts electricity.
Exceptions to memorise: Hg (liquid metal), graphite (conductor), diamond (hard), iodine (shiny). Memory clue : "MDS" : Malleable, Ductile, Sonorous = metals.
Spot the difference
| Point | Metals | Non-metals |
|---|---|---|
| Surface | lustrous | dull |
| Strength | malleable, ductile | brittle |
| Conduction | good | poor |
Practice questions
- 1What is meant by malleable?
- 2Name the liquid metal at room temperature.
- 3Which non-metal conducts electricity?
- 4Why are cooking vessels made of copper or aluminium?
- 5Why can sodium be cut with a knife even though it is a metal?
- 6Give one use each of ductility and sonority.
- 7A shiny solid is brittle and breaks when hammered. Is it a metal? Explain.
- 8Explain why graphite is used in electrodes while diamond is not.
Show answers (try them yourself first)
- 1Can be beaten into thin sheets.
- 2Mercury
- 3Graphite
- 4They conduct heat well.
- 5It is a very soft metal.
- 6Wires; bells
- 7Probably not; metals are not brittle (could be iodine or similar).
- 8Graphite conducts; diamond does not.
Chemical properties of metals
Sodium is kept under kerosene because it catches fire in air, while gold stays shiny for centuries.
Metals react with oxygen to form metal oxides (basic), with water to give hydroxide/oxide + hydrogen, and with dilute acids to give salt + hydrogen. Their reactivity differs from metal to metal.
Equation / formula : 2Mg + O₂ → 2MgO. 2Na + 2H₂O → 2NaOH + H₂. Zn + H₂SO₄ → ZnSO₄ + H₂. Metal oxides that react with both acids and bases are called amphoteric (Al₂O₃, ZnO).
In the figure : Cu, Ag, Au do not react with water or dilute HCl.
Rule 1 : Reaction with oxygen and water — Very reactive metals react with cold water; middle ones with hot water or steam; low ones not at all.
- Easy : 4Na + O₂ → 2Na₂O ; Ca + 2H₂O → Ca(OH)₂ + H₂
- Medium : Magnesium reacts slowly with hot water: Mg + 2H₂O → Mg(OH)₂ + H₂.
- For exams : Steam: 2Al + 3H₂O → Al₂O₃ + 3H₂ ; 3Fe + 4H₂O → Fe₃O₄ + 4H₂. Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O and Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O (amphoteric).
Rule 2 : Reaction with acids — Metals above hydrogen displace it from dilute acids. Copper, silver, gold do not.
- Easy : Mg + 2HCl → MgCl₂ + H₂
- Medium : Fe + H₂SO₄ → FeSO₄ + H₂
- For exams : Nitric acid is a strong oxidiser, so hydrogen is not evolved (it gives nitrogen oxides). Aqua regia (3 HCl : 1 HNO₃) dissolves gold and platinum.
Sodium and potassium are stored under kerosene because they react violently with air and water.
Writing Fe + HCl → FeCl₃ + H₂. Iron gives FeCl₂ with dilute HCl.
Metal + acid → salt + hydrogen (if metal is above H). Memory clue : "Oxide, Water, Acid, Salt" (OWAS): the four reactions.
Spot the difference
| Point | Basic oxide | Amphoteric oxide |
|---|---|---|
| Reacts with | acids only | acids and bases |
| Example | MgO, CuO | Al₂O₃, ZnO |
Practice questions
- 1Why is sodium kept in kerosene?
- 2Write the reaction of magnesium with oxygen.
- 3Name the gas formed when metals react with dilute acid.
- 4What are amphoteric oxides? Give two examples.
- 5Write the equation of iron reacting with steam.
- 6Why does copper not give hydrogen with dilute HCl?
- 7What is aqua regia and why is it special?
- 8Predict the product when Al₂O₃ is added to sodium hydroxide and explain the term.
Show answers (try them yourself first)
- 1It reacts violently with air and water.
- 22Mg + O₂ → 2MgO
- 3Hydrogen
- 4Oxides reacting with both acids and bases; Al₂O₃, ZnO.
- 53Fe + 4H₂O → Fe₃O₄ + 4H₂
- 6Copper is below hydrogen in reactivity.
- 73 HCl : 1 HNO₃; dissolves gold and platinum.
- 8NaAlO₂ (sodium aluminate) + water; it shows basic-type reaction, so Al₂O₃ is amphoteric.
Reactivity series & displacement reactions
An iron nail in blue copper sulphate gets a red-brown coat of copper, but a copper coin in iron sulphate stays unchanged.
The reactivity series arranges metals from most to least reactive. A more reactive metal displaces a less reactive metal from its salt solution. Metals above hydrogen displace it from dilute acids.
Equation / formula : K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au. Fe + CuSO₄ → FeSO₄ + Cu. Cu + FeSO₄ → no reaction.
In the figure : Higher in the list means a stronger tendency to lose electrons.
Rule 1 : Predicting displacement — Locate both metals in the series. The higher one displaces the lower one.
- Easy : Zn + CuSO₄ → ZnSO₄ + Cu (zinc is above copper).
- Medium : Ag + ZnSO₄ → no reaction (silver is below zinc).
- For exams : Thermite: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe + heat. Aluminium is above iron, so it takes the oxygen; the molten iron welds rail tracks.
Rule 2 : Using observations to build a series — If A displaces B, then A is more reactive than B.
- Easy : P displaces Q; so P > Q.
- Medium : If P displaces Q and Q displaces R, then P > Q > R.
- For exams : Fe + PbNO₃ type tests: use the displaced colour (grey lead, red-brown copper) as evidence.
Hydrogen is not a metal but is placed in the series as a reference.
Using the reactivity series for non-metals or reversing it. K is at the top, not Au.
Learn it as a sentence and always write the equation after checking position. Memory clue : "Please Stop Calling Me A Careless Zebra; Instead Try Learning How Copper Saves Gold": K Na Ca Mg Al Zn Fe Pb H Cu Hg Ag Au (use your own funny line).
Spot the difference
| Point | Above H | Below H |
|---|---|---|
| With dilute acid | gives H₂ | no H₂ |
| Example | Zn, Fe, Mg | Cu, Ag, Au |
Practice questions
- 1Which is more reactive: Zn or Cu?
- 2Will copper displace iron from FeSO₄? Why?
- 3Write the equation of Zn with CuSO₄.
- 4Name two metals that do not react with dilute HCl.
- 5Why is aluminium used in the thermite reaction?
- 6A displaces B from its solution, and B displaces C. Arrange A, B, C in decreasing reactivity.
- 7A student puts a zinc strip in a solution and sees silvery-grey coating. Which metal ion may be in the solution?
- 8Explain why the iron nail turns brown while the blue colour of CuSO₄ fades.
Show answers (try them yourself first)
- 1Zn
- 2No; copper is below iron.
- 3Zn + CuSO₄ → ZnSO₄ + Cu
- 4Cu, Ag, Au (any two)
- 5It is more reactive than iron and takes oxygen from Fe₂O₃.
- 6A > B > C
- 7Lead or silver ion (silvery-grey coating).
- 8Iron displaces copper (brown deposit) and Cu²⁺ becomes Fe²⁺.
Ionic compounds
Table salt is hard, melts only at a very high temperature and dissolves in water to give a solution that conducts.
An ionic bond forms when a metal atom loses electrons to become a positive ion (cation) and a non-metal atom gains them to become a negative ion (anion); the opposite charges attract. A compound made like this is an ionic compound.
Equation / formula : Na (2,8,1) → Na⁺ (2,8) + e⁻. Cl (2,8,7) + e⁻ → Cl⁻ (2,8,8). Na⁺ + Cl⁻ → NaCl. MgCl₂: Mg loses 2 e⁻, each Cl gains 1 e⁻.
In the figure : One electron moves from sodium to chlorine; both reach a stable octet.
Rule 1 : Writing electron transfer — Metals (1–3 valence electrons) lose them; non-metals (5–7) gain to complete eight.
- Easy : Na → Na⁺ + e⁻ ; Cl + e⁻ → Cl⁻
- Medium : Mg → Mg²⁺ + 2e⁻ ; O + 2e⁻ → O²⁻ ⇒ MgO
- For exams : MgCl₂: one Mg gives 2 e⁻ to two Cl atoms, so formula is MgCl₂ (total charge zero: +2 −1 −1).
Rule 2 : Properties of ionic compounds — Strong attraction makes them hard solids with high melting and boiling points. Ions move only when molten or dissolved.
- Easy : Solid NaCl does not conduct; molten or aqueous NaCl does.
- Medium : They dissolve in water but usually not in kerosene or petrol.
- For exams : NaCl melts at about 1074 K, which shows strong forces between ions; they are brittle and break when struck.
The metal forms a cation and keeps the name; the non-metal anion ends in "-ide" (chloride, oxide).
Saying NaCl exists as single molecules. In the crystal each Na⁺ is surrounded by six Cl⁻ and vice versa.
Lose → positive. Gain → negative. Total charge = 0. Memory clue : "LEO the lion says GER": Loss of Electrons = Oxidation; Gain of Electrons = Reduction.
Spot the difference
| Point | Ionic compound | Covalent compound |
|---|---|---|
| Melting point | high | low |
| Conduction | molten/aq. only | usually none |
Practice questions
- 1Define ionic bond.
- 2Write the ion formed by sodium.
- 3Why does solid NaCl not conduct electricity?
- 4Write the electron transfer in formation of MgO.
- 5Why do ionic compounds have high melting points?
- 6Why is the formula of calcium chloride CaCl₂?
- 7A solid is hard, melts at 800 °C, conducts only when molten. Name its bond type.
- 8Compare how Na and Mg reach a stable electron arrangement.
Show answers (try them yourself first)
- 1Bond formed by transfer of electrons from metal to non-metal.
- 2Na⁺
- 3Ions are fixed in the solid.
- 4Mg → Mg²⁺ + 2e⁻ ; O + 2e⁻ → O²⁻
- 5Strong attraction between ions.
- 6Ca gives 2 e⁻; each Cl takes 1.
- 7Ionic
- 8Na loses 1 e⁻ (Na⁺); Mg loses 2 e⁻ (Mg²⁺); both get the neon arrangement 2,8.
Extraction of metals, corrosion & alloys
Aluminium foil, iron girders and gold jewellery all come from ores, but each is extracted differently.
An ore is a mineral from which a metal can be extracted profitably. The method depends on reactivity. Metals are purified by electrolytic refining. An alloy is a homogeneous mixture of a metal with another metal or non-metal.
Equation / formula : Top (K, Na, Ca, Mg, Al): electrolysis of molten compound. Middle (Zn, Fe, Pb, Cu): roast/calcine → reduce with carbon. Bottom (Hg, Ag, Au): heat or found free.
In the figure : The more reactive the metal, the stronger the method needed to separate it from its compound.
Rule 1 : Middle metals: roasting and reduction — Sulphide ores are roasted (heated in air) to oxides; carbonate ores are calcined (heated without air); then oxides are reduced with carbon.
- Easy : 2ZnS + 3O₂ → 2ZnO + 2SO₂ ; ZnO + C → Zn + CO
- Medium : ZnCO₃ → ZnO + CO₂ ; 2PbO + C → 2Pb + CO₂
- For exams : Mercury: 2HgS + 3O₂ → 2HgO + 2SO₂, then 2HgO → 2Hg + O₂ on heating. Al: electrolysis of molten Al₂O₃ (cathode: Al, anode: O₂).
Rule 2 : Refining, corrosion and alloys — In electrolytic refining, impure metal is the anode, pure metal the cathode, and a salt solution of the metal is the electrolyte.
- Easy : Brass = Cu + Zn; bronze = Cu + Sn; solder = Pb + Sn.
- Medium : Alloys are harder and resist corrosion; stainless steel has Fe + Ni + Cr + C.
- For exams : Pure gold is 24 carat; 22-carat jewellery has gold with copper or silver for strength. Rust prevention for iron: paint, oil, galvanising.
Gangue is the earthy impurity in an ore; it is removed before extraction.
Confusing roasting (in air) with calcination (without air).
Very reactive → electrolysis. Medium → carbon. Low → heat. Memory clue : "Electro, Carbon, Heat": top-middle-bottom of the series.
Spot the difference
| Point | Roasting | Calcination |
|---|---|---|
| Air | present | absent |
| Ore type | sulphide | carbonate |
Practice questions
- 1What is an ore?
- 2How is sodium extracted?
- 3Write the reduction of ZnO with carbon.
- 4Name the alloy of copper and zinc.
- 5In electrolytic refining of copper, what are the anode, cathode and electrolyte?
- 6Why is aluminium extracted by electrolysis and not by carbon reduction?
- 7Why is iron mixed with carbon, nickel and chromium?
- 8Explain extraction of mercury from cinnabar with equations.
Show answers (try them yourself first)
- 1Mineral from which a metal can be profitably extracted.
- 2Electrolysis of molten NaCl
- 3ZnO + C → Zn + CO
- 4Brass
- 5Anode: impure Cu; cathode: pure Cu; electrolyte: acidified CuSO₄
- 6It is more reactive than carbon.
- 7To make stainless steel which does not rust.
- 8Roast HgS to HgO; heat HgO to Hg.
Extraction of metals, corrosion & alloys
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