Group 1 (Alkali Metals)

Group 1 elements

Lithium, sodium, potassium, rubidium, caesium, francium

Valence electrons

1 electron in outer shell

Reactivity trend

Increases down the group

Reason reactivity increases

Outer electron further from nucleus, easier to lose

Type of ions formed

+1 ions

General reaction

Alkali metal + water → metal hydroxide + hydrogen

Lithium + water

Gentle fizzing, forms lithium hydroxide

Sodium + water

Melts into a ball, moves on surface, forms sodium hydroxide

Potassium + water

Burns with lilac flame, forms potassium hydroxide

Hydrogen test

Squeaky pop with lit splint

Metal hydroxides

Alkaline solutions (high pH)

Reaction with oxygen

Forms metal oxides

Lithium in air

Burns red flame → lithium oxide

Sodium in air

Burns yellow flame → sodium oxide/peroxide

Potassium in air

Burns lilac flame → potassium oxide/peroxide

Softness trend

Metals become softer down the group

Density trend

Increases down the group (except potassium anomaly)

Melting/boiling points

Decrease down the group

Stored in oil

Prevents reaction with oxygen and moisture

Appearance

Shiny when cut, quickly tarnish in air