This key facts covers Physical Properties within Group 1: Alkali Metals for GCSE Chemistry. Revise Group 1: Alkali Metals in Atomic Structure for GCSE Chemistry with 22 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 5 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
📌 Physical Properties
Alkali metals are unusual for metals:
- Soft — can be cut with a knife!
- Low density — Li, Na, K float on water
- Low melting points — much lower than typical metals
- Shiny when fresh — but quickly tarnish in air
Trends down the group:
- Melting point decreases
- Density increases (but Li, Na, and K are all still less dense than water — which is why all three float on its surface)
- Reactivity increases
Practice questions for Group 1: Alkali Metals
How many electrons do alkali metals have in their outermost shell?
Explain why potassium is more reactive than sodium when it reacts with water.
Quick recall flashcards
More reactive: Li or K?
Potassium (further down = more reactive)
Equation: sodium + water →
2Na + 2H₂O → 2NaOH + H₂