2. Group 1 Alkali Metals
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Do alkali metals form acidic or alkali solutions when reacted with water?
Alkali
Alkali metal properties
• They are all soft metals which can easily be cut with a knife (decreases down). • They have relatively low densities (increases down) and low melting points (decreases down) • They are very reactive (they only need to lose one electron to become highly stable) (increases down).
Alkali metals reactions with water
Group 1 metal + water ⟶ metal hydroxide + hydrogen All metal hydroxides for group one are soluble
Alkali metals reactions with oxygen
Group 1 metal + oxygen⟶ metal oxide
Lithium observations with water
• Relatively slow reaction • Fizzing • Lithium moves on the surface of the water
Sodium observations with water
• Sodium moves (on the surface) • Sodium turns into a sphere/ball • Effervescence • Sodium gets smaller and disappears • White trail seen
Potassium observations with water
• Reacts more vigorously than sodium • Burns with a lilac flame • Moves very rapidly on the surface • Dissolves very quickly
Why does reactivity increase as you go down group 1?
• As you go down Group 1, the number of shells of electrons increases by 1 • This means that the outermost electron gets further away from the nucleus, so there are weaker forces of attraction between the outermost electron and the nucleus • More electron shielding • Less energy is required to overcome the force of attraction as it gets weaker, so the outer electron is lost more easily