With WATER:
alkali metal + water → metal hydroxide + hydrogen
Example: 2Na + 2H₂O → 2NaOH + H₂
- Lithium — fizzes gently, moves slowly
- Sodium — fizzes vigorously, melts into a ball, darts around
- Potassium — fizzes violently, lilac flame, may explode
With OXYGEN:
alkali metal + oxygen → metal oxide
Example: 4Li + O₂ → 2Li₂O
This is why they're stored under oil — to prevent reaction with air!
With CHLORINE:
alkali metal + chlorine → metal chloride
Example: 2Na + Cl₂ → 2NaCl
Also: 2Li + Cl₂ → 2LiCl and 2K + Cl₂ → 2KCl
Alkali metals react vigorously with chlorine gas to produce white crystalline metal chloride salts. The reaction demonstrates the same electron transfer principle as the reaction with water: the alkali metal loses its 1 outer electron to become a +1 ion, while each chlorine atom gains 1 electron to become a -1 ion (Cl⁻). Sodium chloride (common table salt) is the most familiar product. The reactivity with chlorine follows the same trend as reactions with water and oxygen — potassium reacts most vigorously, lithium least vigorously.
Quick Check: Write a word equation for the reaction of potassium with water.
potassium + water → potassium hydroxide + hydrogen. The symbol equation is: 2K + 2H₂O → 2KOH + H₂
This key facts covers Reactions of Alkali Metals 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 6 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
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.