Extracting metals from their ores
2 marks · HardExplain why copper can sometimes be found as the uncombined element in the Earth's crust, but sodium cannot.
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Also accept: Copper is less reactive than sodium so it does not react easily and can be found uncombined, but sodium is very reactive and always forms compounds.; Copper is unreactive so found uncombined; sodium is very reactive so is always in compounds.
Common mistakes: Saying both can be found as uncombined elements.; Saying copper is more reactive than sodium.
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Marking points
B1 · 1 mark · States that copper is unreactive (or less reactive than sodium, or is low in reactivity series).
B2 · 1 mark · States that sodium is very reactive and so is always found as a compound, not as an uncombined metal.
Worked solution
Copper is much less reactive than sodium, so it does not easily react with other elements and can be found as the uncombined element. Sodium is very reactive, so it quickly forms compounds and never exists as an uncombined metal in the Earth's crust.