Knowledge Organiser: Group 1 Alkali Metals
Key Terms
- Alkali metals: Group 1, 1 outer electron
- Reactivity trend: Increases down Group 1
- Shielding: Inner electrons reduce nuclear pull
- Metal hydroxide: Product of water reaction
Must-Know Facts
- Soft, low density, low melting point
- Stored under oil (prevent air/water reaction)
- React with water → hydroxide + hydrogen
- 2Na + 2H₂O → 2NaOH + H₂
- React with chlorine → metal chloride (e.g., 2Na + Cl₂ → 2NaCl)
- Li: gentle fizz; Na: vigorous; K: lilac flame
- Reactivity increases ↓ (outer electron further, weaker attraction)
Key Equations
- 2Li + 2H₂O → 2LiOH + H₂
- 2Na + 2H₂O → 2NaOH + H₂
- 2K + 2H₂O → 2KOH + H₂
- 2Na + Cl₂ → 2NaCl
Common Mistakes
- Forgetting hydrogen gas is produced: Alkali metals + water → metal hydroxide AND hydrogen — both products are needed for full marks
- Saying reactivity decreases down Group 1: It increases — the outer electron is further from the nucleus and more easily lost
- Missing the 2 coefficient: The equation is 2Na + 2H₂O → 2NaOH + H₂ — students often write Na + H₂O → NaOH + H
- Saying melting points increase down Group 1: They decrease — larger atoms have weaker metallic bonding
Memory Aid
- "LiNaK RbCs Fr" — Li-Na-K-Rb-Cs-Fr — the Group 1 elements in order. "Little Naughty Kids Roam Cities Freely" helps recall: Lithium, Sodium (Na), Potassium (K), Rubidium, Caesium, Francium.
- Reactivity trend: "Bigger = Looser = More Reactive" — as atoms get bigger down the group, the outer electron is held more loosely, so the element is more reactive.
- Water reaction product: "Alkali metal + Water = HOH (metal Hydroxide + Hydrogen)" — always produces a hydroxide and hydrogen gas.