Alkali metals
The soft, reactive metals of group 1: lithium, sodium and potassium. They react with water to make an alkaline solution and hydrogen.
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Analogy
They are like over-eager party guests: the further down the group, the faster they rush in.
Example
Sodium + water -> sodium hydroxide + hydrogenThe solution turns universal indicator purple.
In practice
Potassium reacts faster with water than lithium and can burst into a lilac flame.
Practice
Flashcards
- How does reactivity change down group 1?It increases. Potassium is more reactive than lithium.
Interview questions
- Explain why the elements in group 1 have similar chemical properties and why reactivity increases down the group.
- Same number of outer electrons (one)
- Each loses one electron to react
- Lower in the group the outer electron is further from the nucleus
- Less attraction so electron is lost more easily
Questions people ask
Why are alkali metals stored under oil?
They react quickly with oxygen and water vapour in air, forming a dull crust on the surface. Storing them under oil keeps air and moisture out. This stops the metal from tarnishing or reacting. Potassium is especially reactive, so it must be handled with great care.
Why do alkali metals have low melting points compared with other metals?
They have only one outer electron, so the bonds holding the metal together are weak. Less energy is needed to break them apart. Going down the group, the atoms get larger and the bonds weaker, so melting points drop further. Lithium melts higher than caesium.