Ch 3 compares the physical and chemical properties of metals and non-metals, introduces ionic bonding, the reactivity series, methods of metal extraction, and practical concepts like corrosion and alloys.
Metals: shiny (lustre), hard, high melting/boiling points, malleable (can be hammered), ductile (can be drawn into wires), good conductors of heat and electricity. Exceptions: mercury is liquid, sodium is soft. Non-metals: dull, brittle, low density, poor conductors. Exceptions: diamond is hard, graphite conducts.
Metals react with oxygen → metal oxides (basic). Metals react with water → metal hydroxide + H₂ (Na reacts vigorously; Fe only with steam). Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au. More reactive metal displaces less reactive from its salt solution. Ionic bonding: metal transfers electrons to non-metal → ions held by electrostatic attraction.
Extraction depends on reactivity: low reactivity (Au, Ag) — found free/just heating. Medium (Fe, Zn) — roasting or calcination then reduction with carbon. High (Na, K, Al) — electrolytic reduction. Corrosion: surface of metal is slowly eaten by air/moisture (rusting of iron, green coating on copper). Prevention: painting, oiling, galvanising, alloying, electroplating.
Download: https://ncert.nic.in/textbook/pdf/jesc103.pdf | Complete book: https://ncert.nic.in/textbook/pdf/jesc1ps.zip
Galvanising means coating iron with a layer of zinc. Zinc is more reactive than iron, so it gets oxidised first (sacrificial protection) even if the coating is scratched. This prevents rusting of the iron underneath. Galvanised iron is used for buckets, pipes, and roofing sheets.
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