Learning Objectives
- Compare physical and chemical properties of metals and non-metals
- Understand the reactivity series of metals
- Learn about ionic bond formation
- Understand extraction of metals from ores
- Learn about corrosion and its prevention
Key Concepts
Physical Properties of Metals vs Non-metals
- Metals: Lustrous, malleable, ductile, good conductors of heat and electricity, generally solid at room temperature (exception: mercury is liquid), sonorous.
- Non-metals: Non-lustrous (except iodine and graphite), brittle, non-ductile, poor conductors (except graphite), can be solids, liquids, or gases.
Chemical Properties of Metals
Reaction with oxygen: Metal + O₂ → Metal oxide (basic in nature). Example: 4Na + O₂ → 2Na₂O
Reaction with water: Varies by reactivity. Na and K react vigorously; Mg reacts with hot water; Fe with steam; Cu, Au, Ag do not react.
Reaction with acids: Metal + Acid → Salt + H₂. More reactive metals react vigorously. Cu, Ag, Au do not react with dilute acids.
Reactivity Series
K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > (H) > Cu > Hg > Ag > Au > Pt
A more reactive metal can displace a less reactive metal from its salt solution.
Ionic Bonding
Metals lose electrons to form cations (M → M⁺ + e⁻). Non-metals gain electrons to form anions. The electrostatic attraction between cations and anions forms an ionic bond. Ionic compounds have high melting/boiling points, are soluble in water, and conduct electricity in molten or aqueous state.
Extraction of Metals
- Low reactivity (Cu, Ag, Au): Found free or extracted by heating oxide in air.
- Medium reactivity (Fe, Zn, Pb): Roasting or calcination, then reduction with carbon.
- High reactivity (Na, K, Ca, Al): Electrolytic reduction.
Refining: Electrolytic refining purifies crude metal using electrolysis.
Corrosion and Prevention
Corrosion is the slow degradation of metals due to reaction with the environment. Prevention methods: painting, oiling, greasing, galvanising (zinc coating), alloying, chrome plating.
Summary
Metals and non-metals differ in physical and chemical properties. The reactivity series ranks metals by their tendency to lose electrons. Ionic bonds form between metals and non-metals through electron transfer. Metal extraction depends on reactivity level. Corrosion can be prevented by protective coatings and alloying.
Important Terms
- Ore
- A naturally occurring mineral from which a metal can be profitably extracted
- Gangue
- Impurities (sand, clay, rocks) present in the ore
- Alloy
- A homogeneous mixture of a metal with other metals or non-metals
- Galvanisation
- Coating iron with zinc to prevent rusting
- Anodising
- Forming a thick oxide layer on aluminium for corrosion resistance
Quick Revision
- Metals are lustrous, malleable, ductile, and good conductors; non-metals are opposite
- Reactivity series: K, Na, Ca, Mg, Al, Zn, Fe... Cu, Ag, Au, Pt (decreasing)
- Ionic compounds have high melting points, conduct electricity when dissolved/molten
- Extraction method depends on reactivity: electrolysis for most reactive, carbon reduction for moderate, heating for least reactive
- Galvanisation, alloying, painting, and oiling prevent corrosion
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