Metal Oxides & The Reactivity Series

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Metal oxides

Metals react with oxygen to make metal oxides: $2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$
These are oxidation reactions, because the metal gains oxygen
Reduction is the opposite: loss of oxygen. In $\text{CuO} + \text{H}_2 \rightarrow \text{Cu} + \text{H}_2\text{O}$ the copper oxide is reduced and the hydrogen is oxidised
A reaction where one substance is oxidised and another reduced is a redox reaction

The reactivity series

When metals react they form positive ions. A metal's reactivity is its tendency to form its positive ion: the more easily it loses electrons, the more reactive it is
Metals are ordered by their reactions with water and dilute acids. Hydrogen and carbon are included as markers

Metal	With cold water	With dilute acid
Potassium	very vigorous, ignites, lilac flame	explosive, not done
Sodium	vigorous, fizzes, melts into a ball	explosive, not done
Lithium	fizzes steadily	explosive, not done
Calcium	fizzes, solution goes cloudy	very vigorous fizzing
Magnesium	very slow, a few bubbles over days	fast fizzing, gets hot
Zinc	no reaction	steady fizzing
Iron	no reaction	slow fizzing
Copper	no reaction	no reaction

Metals above hydrogen react with acids to give hydrogen; copper is below hydrogen and does not react
Metals above carbon (potassium to aluminium) cannot be extracted with carbon; those below it can
With water the products are the metal hydroxide and hydrogen; with acid, a salt and hydrogen: $\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2$

The reactivity series as a vertical list from potassium down to copper, with carbon and hydrogen inserted in their places, and brackets showing which metals react with water, which with acid, and which can be extracted by carbon

Displacement reactions

A more reactive metal displaces a less reactive metal from a compound, because it forms positive ions more readily
$\text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu}$ : the blue solution fades and brown copper forms on the zinc
To deduce an order from results: a metal that displaces another is more reactive than it; a metal that reacts faster with acid is more reactive. Work through each result in turn and chain them together