The reactivity series of metals

In a nutshell

Metals react with non-metals, such as water, oxygen and acid, to form ionic compounds.

Equations

REACTANTS		PRODUCTS
$metal + water$	$\rightarrow$	$metal \space hydroxide + hydrogen$
$metal + acid$	$\rightarrow$	$metal \space salt + hydrogen$
$metal + oxygen$	$\rightarrow$	$metal \space oxide$

The reactivity series

The reactivity series places elements in order of most reactive to least reactive. The tendency of a metal to lose electron(s) from its outer shell and form positive ions is related to its reactivity. This means that the more easily a metal loses electron(s) from its outer shell, the more reactive it is. A reactivity series of metals, relative to two non-metals (hydrogen and carbon) can be seen below.

Chemistry; Extracting metals and equilibria; KS4 Year 10; The reactivity series of metals

Example

Why is potassium more reactive than lithium?

Both potassium and lithium are in Group $1$ , but potassium is more reactive than lithium because it is larger, with more electron shells. This means that the outer electron is further away and less attracted to the nucleus so it is easier to 'lose' the outer electron in potassium, compared to lithium.

Reactions with water, acid and oxygen

Metals form ionic compounds by losing electrons to non-metals. By doing so, the metal forms a positive ion and the non-metal forms a negative ion. The electrostatic forces of attraction between these oppositely charged ions is an ionic bond.

Metal and water

When a metal reacts with water, a metal hydroxide and hydrogen are produced.

$metal + water\rightarrow metal~ hydroxide + hydrogen$

PROCEDURE

1.	Identify the metal
2.	Write down the reactants for the equation
3.	Draw an arrow going to the right
4.	The metal hydroxide will be the metal identified plus the word hydroxide
5.	Write down the products for the equation

Example

Write down the word and symbol equation for when calcium and water react.

$calcium + water → calcium~ hydroxide + hydrogen$

$Ca + 2H_2O\rightarrow Ca(OH)_2 + H_2$

Metal and acid

When metal and acid react they form a metal salt and hydrogen.

$metal + acid → metal ~salt + hydrogen$

PROCEDURE

1.	Identify the acid and the metal
2.	Write down the reactants for the equations
3.	Draw an arrow going to the right
4.	The metal salt name will be the metal plus the conjugate of the acid
5.	Write down the products for the equation

Hint: Make sure you know which conjugate and acids are pairs.

ACID		CONJUGATE
$hydrochloric \space acid$	$\rightarrow$	$chloride$
$nitric \space acid$	$\rightarrow$	$nitrate$
$sulfuric \space acid$	$\rightarrow$	$sulfate$

Example

Write down the word and symbol equation for when calcium and hydrochloric acid react.

$calcium + hydrochloric~ acid \rightarrow calcium ~chloride + hydrogen$

$Ca + 2HCl\rightarrow CaCl_2 + H_2$

Metal and oxygen

When metal and oxygen react they form a metal oxide.

$metal + oxygen \rightarrow metal ~ oxide$

PROCEDURE

1.	Identify the metal
2.	Write down the reactants for the equation
3.	Draw an arrow going to the right
3.	The metal oxide will be the name of the metal plus oxide
4.	Write down the products for the equation

Example

Write down the word and symbol equation for when magnesium and oxygen react.

$magnesium + oxygen \rightarrow magnesium ~oxide~$

$2Mg+O_2 \rightarrow 2MgO$

In this reaction, magnesium is oxidised. Oxidation is the loss of electrons and gain of oxygen.

Displacement reactions

In a displacement reaction, a more reactive metal displaces a less reactive metal in its ionic compound. It essentially 'kicks' the less reactive metal out of its compound.

Example

Write down the word and symbol equation for when zinc oxide and calcium react.

$zinc ~oxide + calcium \rightarrow calcium ~oxide + zinc$

$ZnO + Ca \rightarrow CaO + Zn$

In this reaction, zinc is reduced. Reduction is the gain of electrons and loss of oxygen.

Note: The mnemonic OILRIG can be used to learn the difference between reduction and oxidation. This is because Oxidation Is Loss and Reduction Is Gain (of electrons).