Lithium, sodium, potassium (then rubidium, caesium, francium)
They all have one electron in the outer shell , which they lose in
reactions to form + 1 +1 + 1
Soft metals with low densities and low melting points for metals
Reaction
What happens
Products
With oxygen burn to form a white metal oxide
4 Na + O 2 → 2 Na 2 O 4\text{Na} + \text{O}_2 \rightarrow 2\text{Na}_2\text{O} 4 Na + O 2 → 2 Na 2 O
With chlorine react vigorously to form a white metal chloride
2 Na + Cl 2 → 2 NaCl 2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl} 2 Na + Cl 2 → 2 NaCl
With water fizz, move on the surface, form an alkaline solution
2 Na + 2 H 2 O → 2 NaOH + H 2 2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 2 Na + 2 H 2 O → 2 NaOH + H 2
Observations with water: the metal floats , fizzes (hydrogen
gas), moves around, and may melt into a ball ; potassium burns with a
lilac flame . The solution turns universal indicator purple because a
metal hydroxide is made
Reactivity increases down the group: lithium fizzes gently, sodium
fizzes and melts, potassium bursts into flameWhy, in three steps:
Further down, the atom is larger, so the outer electron is further from
the nucleus
There are more inner shells shielding it from the nucleus
So the attraction between the nucleus and the outer electron is
weaker , and the electron is lost more easily
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Group 1 — why reactivity increases down the group red arrow = distance from the nucleus to the outer electron Li lithium (2,1) 2 shells Na sodium (2,8,1) 3 shells K potassium (2,8,8,1) 4 shells down the group: more inner shells, outer electron further from the nucleus The outer electron is further away and shielded by more inner shells, so it is held less strongly. It is lost more easily, so the metal is more reactive. Lithium, sodium and potassium atoms drawn to scale showing the outer electron getting further from the nucleus down the group, with more inner shells in between
The products of a Group 1 metal with water are the metal hydroxide
and hydrogen . Not the oxide, and not just "an alkali"
When explaining the trend, name the electron: "the outer electron is
further from the nucleus". "The electrons are further away" loses the mark.
And the force is the attraction between nucleus and outer electron:
not "intermolecular", not "magnetic"
Asked how a more reactive metal's reaction would differ, give a specific
observation: bursts into flame, moves faster, melts. "More violent" scores
nothing
The rest of this topic is in the full Exam Guide The complete AQA GCSE Chemistry guide — every topic, exam checklist and common mistake — is coming soon. Until then, the first topic in every unit is free to read.
In the full topic
• Group 1, the alkali metals• Group 7, the halogens• Halogen displacement reactionsRead the free chemistry topics →