GCSE Chemistry revision

Group 1

The periodic table

AQA 4.1.2.5 Foundation & Higher

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All alkali metals have one electron in their outermost shell because they are in Group 1, making it easy to lose that single electron to achieve a stable, full outer shell.
When an alkali metal loses its one outer electron, it forms a 1+ ion, which is energetically favourable and drives their high reactivity.
Reactivity describes how easily an atom can lose or gain electrons in order to react with other atoms.

1. Why Are Alkali Metals So Reactive? AQA

All alkali metals have one electron in their outermost shell because they are in Group 1, making it easy to lose that single electron to achieve a stable, full outer shell.
When an alkali metal loses its one outer electron, it forms a 1+ ion, which is energetically favourable and drives their high reactivity.
Reactivity describes how easily an atom can lose or gain electrons in order to react with other atoms.

Because alkali metals lose their outer electrons so easily, they almost always form ionic compounds with non-metals.
In ionic bonding, a metal atom such as sodium donates an electron to a non-metal such as chlorine, so both achieve full outer shells.
The resulting oppositely charged ions are held together by electrostatic forces, forming an ionic bond.
Ionic compounds formed by alkali metals are generally white solids that dissolve in water to form colourless solutions.

2. Ionic Compounds Formed by Alkali Metals AQA

Because alkali metals lose their outer electrons so easily, they almost always form ionic compounds with non-metals.
In ionic bonding, a metal atom such as sodium donates an electron to a non-metal such as chlorine, so both achieve full outer shells.
The resulting oppositely charged ions are held together by electrostatic forces, forming an ionic bond.
Ionic compounds formed by alkali metals are generally white solids that dissolve in water to form colourless solutions.

When an alkali metal reacts with water, it produces a metal hydroxide and hydrogen gas; for example: 2Na + 2H₂O → 2NaOH + H₂.
The reactions become more vigorous down the group, and from potassium onwards enough energy is released to ignite the hydrogen gas produced, visible as flames.

3. Reactions of Alkali Metals with Water AQA

When an alkali metal reacts with water, it produces a metal hydroxide and hydrogen gas; for example: 2Na + 2H₂O → 2NaOH + H₂.
The reactions become more vigorous down the group, and from potassium onwards enough energy is released to ignite the hydrogen gas produced, visible as flames.

When alkali metals are heated in chlorine gas, they react vigorously to form white metal chloride salts; for example: 2Na + Cl₂ → 2NaCl.
These reactions with chlorine become more vigorous as you go down Group 1.

Lithium reacts with oxygen to form lithium oxide: 4Li + O₂ → 2Li₂O.
Sodium can react with oxygen to form either sodium oxide (Na₂O) or sodium peroxide (Na₂O₂).
Potassium can react with oxygen to form potassium peroxide (K₂O₂) or potassium superoxide (KO₂).

5. Reactions of Alkali Metals with Oxygen AQA

Lithium reacts with oxygen to form lithium oxide: 4Li + O₂ → 2Li₂O.
Sodium can react with oxygen to form either sodium oxide (Na₂O) or sodium peroxide (Na₂O₂).
Potassium can react with oxygen to form potassium peroxide (K₂O₂) or potassium superoxide (KO₂).

Alkali metals are soft, low-density metals with low melting points that become more reactive and have lower melting/boiling points as you descend Group 1.
Their high reactivity is explained by the ease with which they lose their single outer electron, an effect that increases down the group as the atomic radius grows.
Alkali metals react with water to form hydroxides and hydrogen gas, with chlorine to form metal chloride salts, and with oxygen to form various metal oxides.

6. Summary / Key Terms AQA

Alkali metals are soft, low-density metals with low melting points that become more reactive and have lower melting/boiling points as you descend Group 1.
Their high reactivity is explained by the ease with which they lose their single outer electron, an effect that increases down the group as the atomic radius grows.
Alkali metals react with water to form hydroxides and hydrogen gas, with chlorine to form metal chloride salts, and with oxygen to form various metal oxides.