CC5.1 — Group 1 alkali metals (Edexcel 1SC0)

Alkali metals: Li, Na, K, Rb, Cs, Fr

All Group 1 metals have 1 outer electron → easily lost → forms 1+ ion. Very reactive; soft; low density; store under oil.

Trend in reactivity (increases down group)

As you go down Group 1:

• More electron shells → outer electron further from nucleus.
• More shielding → nuclear attraction on outer electron is weaker.
• Outer electron lost more easily → more reactive.

Reactions with water

Metal + water → metal hydroxide + hydrogen gas 2Na + 2H₂O → 2NaOH + H₂

• Lithium: fizzes gently; floats.
• Sodium: fizzes more vigorously; melts; floats; darting movement.
• Potassium: burns with a lilac flame; very vigorous.

Reactions with oxygen

4Na + O₂ → 2Na₂O (sodium oxide)

Reactions with chlorine

2Na + Cl₂ → 2NaCl (sodium chloride — ionic salt)

Properties of compounds

Alkali metal compounds are generally white ionic solids, soluble in water, with high melting points.