Bauxite (Al₂O₃·2H₂O) is the principal ore of aluminium. Magnetite (Fe₃O₄) and haematite (Fe₂O₃) are iron ores. Zinc blende is ZnS. Bauxite is refined by Bayer's process to obtain pure alumina, which is then electrolyzed in cryolite.
Explanation:
Smelting involves heating the concentrated ore (often after roasting/calcination) with a reducing agent (like coke, CO) to reduce the metal oxide to the metal. For example, iron ore is smelted in a blast furnace. Roasting heats sulfide ores in air; calcination heats carbonate ores in absence of air; leaching dissolves out the metal.
Explanation:
Across period 3, nuclear charge increases (Na: 11+, Cl: 17+) while electrons are added to the same shell. The increased attraction pulls electrons closer, decreasing radius. Na has larger radius despite having fewer electrons.
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