Group 1: properties and reactivity

In a nutshell

Group $1$ metals have a range of properties. They react with non-metals by forming ionic bonds.

Alkali metals

The elements of Group $1$ are called alkali metals because they form alkaline solutions when dissolved in water. Like all metals, they are malleable and can conduct electricity. Group $1$ metal ions can be identified by flame tests.

Flame tests are carried out by dipping a clean, nichrome wire into the metal sample and then passing it through a Bunsen burner with a blue flame.

Group $1$ metal ION	Flame colour
Lithium	Red
Sodium	Yellow
Potassium	Lilac

Chemistry; Groups in the periodic table; KS4 Year 10; Group 1: properties and reactivity

Atomic structure and ionic bonding

Atomic structure

The octet rule specifies that atoms are stable when they have a 'full' outer shell. A full outer shell is equal to eight electrons. Group numbers (columns) in the periodic table tell you how many electrons are in the outer shell of an atom.

A Group $1$ metal atom has one electron in its outer shell and are therefore unstable due to an incomplete outer shell.

Ionic bonding

An ionic bond is formed from electrostatic forces of attraction between oppositely charged ions. Group $1$ metals become stable by reacting with non-metal elements to form ionic compounds. In doing so, a full outer shell is formed. Group $1$ metals lose one electron to form $1+$ ions. This electron is donated to a non-metal which forms a negative ion. This results in the formation of an ionic bond.

Chemistry; Groups in the periodic table; KS4 Year 10; Group 1: properties and reactivity

Lithium bromide ( $LiBr$ ) forms by ionic bonding. The lithium atom donates an electron to bromine, it then becomes a positively charged ion and bromine becomes a negatively charged bromide ion. Electrostatic forces between these oppositely charged ions allows the ionic compound lithium bromide to form.

Trends in reactivity

Reactivity increases down Group $1$ , as the atom size increases down the group. There are therefore more electron shells, so the outer electron is further away from the nucleus as you go down the group. The outer electron is easier to 'lose' because it is less attracted to the nucleus, this increases reactivity down the group.

Reactions

	Oxygen	Water	Chlorine
Lithium	$lithium + oxygen \rightarrow lithium~ oxide$ $4Li + O_2 \rightarrow 2Li_2O$	$lithium + water \rightarrow lithium~ hydroxide + hydrogen$ $2Li + 2H_2O \rightarrow2LiOH + H_2$	$lithium + chlorine \rightarrow lithium~ chloride$ $2Li + Cl_2 \rightarrow 2LiCl$
Sodium	$sodium + oxygen \rightarrow sodium ~oxide$ $4Na + O_2 \rightarrow 2Na_2O$	$sodium + water \rightarrow sodium~ hydroxide + hydrogen$ $2 Na + 2H_2O \rightarrow 2NaOH + H_2$	$sodium + chlorine \rightarrow sodium ~chloride$ $2Na + Cl_2 \rightarrow2NaCl$
Potassium	$potassium + oxygen \rightarrow potassium~ oxide$ $4K + O_2 \rightarrow 2K_2O$	$potassium + water \rightarrow potassium ~hydroxide + hydrogen$ $2K + 2H_2O \rightarrow2KOH + H_2$	$potassium + chlorine\rightarrow potassium~ chloride$ $2K + Cl_2 \rightarrow 2KCl$