Metals and Non Metals — Karnataka (SSLC) Class 10 Science Solutions (Free)

Metals: elements with 1-3 valence electrons, lose electrons to form cations. Non-metals: elements with 4-8 valence electrons, gain/share electrons. Three properties: 1) Lustre: metals shiny, non-metals dull. 2) Malleability: metals can be hammered into sheets, non-metals brittle. 3) Conductivity: metals conduct heat/electricity, non-metals do not (except graphite).

Reactivity series: arrangement of metals by their tendency to lose electrons; more reactive metals are at top. Order (most to least reactive): Al > Fe > Zn > Cu. Al is most reactive (loses electrons easily), Cu is least reactive. This series predicts displacement reactions: a more reactive metal displaces a less reactive one from its salt solution.

Metals react with oxygen to form metal oxides (oxidation). Examples: 1) 2Mg + O2 = 2MgO (burns with bright light, white powder forms). 2) 4Fe + 3O2 = 2Fe2O3 (brown/red powder, requires heating). Less reactive metals like Cu form oxide slowly: 2Cu + O2 = 2CuO (requires heating, turns black). Reactivity affects speed and intensity.

Corrosion = gradual destruction of metal by reaction with environment (O2, H2O, CO2). Iron rusting: 4Fe + 3O2 + 6H2O = 4Fe(OH)3 (brown/orange precipitate). Prevention: 1) Oiling/greasing (prevents water contact). 2) Galvanization (zinc coating protects). 3) Painting (prevents air/water access). 4) Alloys (stainless steel resists corrosion). Rusting is an expensive problem in construction.

Extraction = process of obtaining metals from their ores. Iron: extracted by reduction of iron oxide with carbon monoxide in blast furnace at high temperature (Fe2O3 + 3CO = 2Fe + 3CO2). Aluminum: extracted by electrolysis of molten aluminum oxide in presence of cryolite as flux (electrical energy splits Al2O3 = 2Al + 3/2 O2). Electrolysis is more expensive due to high energy needs.