Relative Reactivities of Metals

The reactivity of metals differs considerably from one metal to another. Some metals, like potassium and sodium, are very reactive and can react violently with water, while metals like gold and platinum are very unreactive and do not easily take part in chemical reactions.
The ‘reactivity series of metals’ is a list that orders metals in accordance to their reactivity, with the most reactive at the top and the least reactive at the bottom. This is remembered through the mnemonic: “Please Stop Calling Me A Cute Zebra, I Think She Likes Hydrogen=Potassium PS: Lithium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Silver, Gold, Platinum.
The reactivity of a metal can be determined by looking at its reactions with water, acid, and displacement reactions with other metals. A more reactive metal will displace a less reactive metal from a compound.
Metals that react with water produce metals hydroxides and hydrogen gas. For example, when potassium reacts with water it forms potassium hydroxide and hydrogen.
Metals that react with acids will produce a salt and hydrogen gas. For instance, when magnesium reacts with hydrochloric acid, it forms magnesium chloride and hydrogen gas.
In a displacement reaction, a more reactive metal will displace a less reactive metal from its oxide, hydroxide, or sulphate. For example, zinc can displace copper from copper sulphate solution to form zinc sulphate and copper.
When metals react with oxygen, the metal is oxidised to form a metal oxide. The ease with which a metal is oxidised is related to its reactivity. The more reactive metals, such as potassium, sodium, lithium, calcium, and magnesium react violently with oxygen.
The reduction process involves the gaining of electrons whereas oxidation involves the loss of electrons. It’s useful to remember the acronyms OIL (Oxidation is Loss) and RIG (Reduction is Gain).
Less reactive metals, like gold and silver, are found naturally in the Earth’s crust as uncombined elements. However, most metals are found as compounds that require chemical reactions to extract the metal.
Carbon can be used to extract metal from metal oxides. The metal oxide is heated with carbon, which acts as a reducing agent to pull the oxygen away from the metal. This method is known as smelting.
The process used to extract metals from their ores is dependent on the reactivity of the metal. Highly reactive metals, such as aluminium and sodium, cannot be extracted using carbon and are extracted using electrolysis instead.
As metals have different reactivities, the method of extraction is based on the reactivity of the metal. The more reactive the metal the harder it is to extract, which is why the most reactive metals such as potassium and sodium are extracted by electrolysis of their salts.