Properties of Group 1 (Alkali Metals) — AQA GCSE Chemistry
Group 1 elements — lithium, sodium, potassium and below — are the reactive alkali metals.
Properties
- They have one electron in their outer shell.
- They are soft and can be cut with a knife, with low melting points (for metals).
- They have low density (lithium, sodium and potassium float on water).
Reactions with water
Alkali metals react vigorously with water to produce hydrogen gas and a metal hydroxide (an alkaline solution): metal + water → metal hydroxide + hydrogen
For example: 2Na + 2H₂O → 2NaOH + H₂. The metal fizzes, moves across the surface, and may catch fire.
Reactivity trend
Reactivity increases down the group (Li < Na < K < …). This is because:
- the outer electron is in a shell further from the nucleus,
- there is more shielding from inner electrons, so
- the outer electron is lost more easily, making the reaction faster.
Forming ions
When alkali metals react, they lose their one outer electron to form a +1 ion (e.g. Na⁺), achieving a full outer shell.
Exam tips
- Group 1 metals have one outer electron and form +1 ions.
- Reaction with water gives metal hydroxide + hydrogen.
- Reactivity increases down the group — explain using distance/shielding.
- They are soft, low density and low melting point compared with most metals.