Properties: the alkali metals are in group one of the periodic table.
The alkali metals are soft (you can cut them with a knife) and they have compartively low melting points (they are easy to melt).
Reactions with water💦
The alkali metals are all in the same group of the periodic table so they all have similar reactions.
They all have one electron in their outer shell, so when they react, each atom looses one electron to become an ion with a +1 charge.
All the alkali metals react with water to form a metal hydroxide and hydrogen gas.
Metal hydroxide solutions are alkaline.
lithum + water → lithium hydroxde + hydrogen
or in symbols → 2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
the more electron shells - the outer electron shell is further from the nucleus for the elements at the bottom of the group.
The reactivity of the alkali metals increases down the group. When they are put in water:
- lithium floats on the surface and fizzes
- sodium melts from the heat produced by the reaction and whizzes around on the surface as a molten ball, and sometimes the hydrogen produced catches fire.
- potassium reacts even faster, and the hydrogen produced burns with a lilac flame.
The elements towards the bottom of the group have more electrons, and so they have more electron shells in their atoms. The outer electrons are further from the nucleus, and so the force between the negatively charged electron and the positvely charged nucleus is weaker. It is much easier to remove the outer electron from a caesium atom that it is to remove the outer electron from a lithium atom, so caesium is much more reactive than lithium.
Drafted by Catrina (Chemistry)