Metals and Non-metals Notes CBSE Class 10
Properties of Metals
Physical Properties:
- Lustrous: Have a shiny surface (metallic lustre).
- Malleable: Can be hammered into thin sheets (e.g., gold, silver).
- Ductile: Can be drawn into thin wires (e.g., gold, silver, copper).
- Good Conductors of Heat and Electricity: Due to the presence of free electrons (e.g., silver, copper are best conductors).
- Sonorous: Produce a ringing sound when struck (e.g., bells).
- Hard: Generally hard (except sodium, potassium, lithium which are soft and can be cut with a knife).
- High Melting and Boiling Points: Generally have high melting and boiling points (except gallium and caesium which melt at room temperature).
- Solid at Room Temperature: Generally exist as solids (except mercury, which is a liquid).
Chemical Properties:
Reaction with Air (Oxygen): Form metal oxides (basic or amphoteric).
Metal + Oxygen → Metal oxide
Example: 2Mg(s) + O2(g) → 2MgO(s) (basic oxide)
Amphoteric oxides (e.g., Al2O3, ZnO) react with both acids and bases.
Some metals (Na, K) react vigorously, others (Mg, Al, Zn, Pb) form a protective oxide layer.
Reaction with Water: Form metal hydroxide and hydrogen gas.
Metal + Water → Metal hydroxide + Hydrogen (or Metal oxide + Hydrogen)
Different metals react with water under different conditions (cold, hot, steam).
Example: 2Na(s)+2H2O(l) → 2NaOH(aq) + H2(g) + Heat
Reaction with Acids: Form salt and hydrogen gas (unless the acid is an oxidizing agent like nitric acid).
Metal + Dilute acid → Salt + Hydrogen
Example: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Reaction with Solutions of Other Metal Salts: A more reactive metal displaces a less reactive metal from its salt solution (based on reactivity series).
Example: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
Properties of Non-metals
Physical Properties:
- Non-lustrous: Generally dull in appearance (except iodine which is lustrous).
- Non-malleable and Non-ductile: Brittle; they break when hammered or stretched.
- Poor Conductors of Heat and Electricity: Generally insulators (except graphite, an allotrope of carbon, which is a good conductor of electricity).
- Non-sonorous: Do not produce a ringing sound.
- Soft: Generally soft (except diamond, an allotrope of carbon, which is the hardest natural substance).
- Low Melting and Boiling Points: Generally have low melting and boiling points.
- Exist in all three states at room temperature: Solid (e.g., carbon, sulphur), Liquid (e.g., bromine), Gas (e.g., oxygen, nitrogen).
Chemical Properties:
Reaction with Oxygen: Form non-metal oxides (acidic or neutral).
Non-metal + Oxygen → Non-metal oxide
Example: C(s) + O2(g) → CO2(g) (acidic oxide)
Acidic oxides dissolve in water to form acids (e.g., CO2 + H2O → H2CO3).
Reaction with Water: Do not react with water or steam.
Reaction with Acids: Do not react with dilute acids.
Reaction with Salt Solutions: Generally do not displace metals from their salt solutions.
Reaction with Chlorine: Non-metals react with chlorine to form covalent chlorides.
Example: H2(g) + Cl2(g) → 2HCl(g)
Reaction with Hydrogen: Non-metals react with hydrogen to form hydrides.
Example: N2(g) + 3H2(g) → 2NH3(g)
Reactivity Series (Activity Series)
A list of metals arranged in the decreasing order of their reactivity.
Significance: Helps in predicting the outcome of displacement reactions. A metal higher in the series can displace a metal lower in the series from its salt solution or from its oxide (in some cases).
Common Series (mnemonic: Kedar Nath Ka Mali Aloo Zara Feeke Pakata Hai, (H) Copper Aur Silver Gold):
K (Potassium) - Most Reactive
Na (Sodium)
Ca (Calcium)
Mg (Magnesium)
Al (Aluminium)
Zn (Zinc)
Fe (Iron)
Pb (Lead)
(H) Hydrogen (Reference point for acid reactions)
Cu (Copper)
Ag (Silver)
Au (Gold) - Least Reactive
Formation and Properties of Ionic Compounds
Formation (Transfer of Electrons):
Formed by the transfer of electrons from a metal (which loses electrons to form positive ions, cations) to a non-metal (which gains electrons to form negative ions, anions).
The electrostatic force of attraction between oppositely charged ions forms the ionic bond.
Example: Formation of NaCl
Na (2, 8, 1) → Na+ (2, 8) + e−
Cl (2, 8, 7) + e− → Cl−(2, 8, 8)
Na+ + Cl− → NaCl
Properties:
Solid and Hard: Exist as solids and are generally hard due to strong electrostatic forces of attraction. Brittle: Break easily when pressure is applied.
High Melting and Boiling Points: A large amount of energy is required to break the strong ionic bonds.
Soluble in Water: Generally soluble in water but insoluble in organic solvents (like petrol, kerosene).
Conduct Electricity in Molten State or Aqueous Solution: In these states, the ions are free to move and carry charge. They do not conduct electricity in the solid state because the ions are held in fixed positions.
Basic Metallurgical Processes
Metallurgy: The science and technology of the extraction of metals from their ores and refining them for use.
Ore: A naturally occurring rock or sediment that contains one or more valuable minerals, typically metals, that can be mined, treated, and sold at a profit.
Gangue: Undesired impurities present in the ore (e.g., sand, rocky materials).
Steps Involved:>
Concentration (Enrichment) of Ore: Removal of gangue from the ore (e.g., hydraulic washing, magnetic separation, froth flotation, leaching).
Conversion of Concentrated Ore to Metal: For highly reactive metals (K, Na, Ca, Mg, Al): Extracted by electrolytic reduction of their molten chlorides or oxides.
For moderately reactive metals (Zn, Fe, Pb, Cu):
1. Calcination: Heating carbonate ores strongly in limited air to convert them to oxides (e.g., ZnCO3 -Heat→ ZnO + CO2).
2. Roasting: Heating sulphide ores strongly in the presence of excess air to convert them to oxides.
2ZnS + 3O2 -Heat→ 2ZnO + 2SO2.
3. Reduction of Metal Oxide to Metal: The metal oxide is then reduced to metal using a suitable reducing agent like carbon (coke) or a more reactive metal.
Example: ZnO(s)+C(s) -Heat→ Zn(s) + CO(g)
Thermite Reaction: Highly reactive metals used as reducing agents.
2Al(s) + Fe2O3(s) → Al2O3(s) + 2Fe(l).
For less reactive metals (Ag, Au, Hg): Can be obtained by heating their sulphide ores alone.
2HgS + 3O2 -Heat 2HgO + 2SO2; then 2HgO -Heat→ 2Hg + O2.
Refining of Metals: Purification of the crude metal (e.g., electrolytic refining - most common method for copper, zinc, tin, nickel, silver, gold).
Corrosion and its Prevention
Corrosion:
The process of slow eating up of metals by the action of air, moisture, or a chemical on their surface. It is essentially an oxidation process. Rusting: The corrosion of iron (formation of reddish-brown flaky substance, hydrated iron(III) oxide, Fe2O3⋅xH2O). Requires both oxygen and water (moisture).
Other Examples: Black coating on silver (due to Ag2S). Green coating on copper (due to basic copper carbonate, CuCO3,⋅Cu(OH)2).
Prevention of Corrosion:
Painting:
Provides a barrier against air and moisture.
Oiling/Greasing: Forms a protective layer, often used for machine parts.
Galvanizing: Coating iron or steel with a thin layer of zinc. Zinc is more reactive and corrodes preferentially (sacrificial protection).
Chrome Plating: Coating with chromium, which is corrosion-resistant and gives a shiny appearance.
Anodising: An electrolytic process to form a thick oxide layer on aluminium, making it more resistant to corrosion.
Alloying: Mixing metals with other metals or non-metals to improve their properties (e.g., stainless steel is more resistant to rust than pure iron).
Tin Plating: Coating with tin (used for food cans).
Electroplating: General method of coating one metal with another using electricity.