Trends found in the alkali metals[edit | edit source]
When moving down the group, the elements in this group show several trends, such as increased reactivity. Alkali metals with a higher atomic number are more reactive as the one electron in their outer shells is further away from the nucleus - the electron's pull towards the nucleus is weaker, hence it is more easily lost from the atom.
Reactions of alkali metals with water[edit | edit source]
Alkali metals are notable for their ability to react strongly with water. When this happens, the products of the reaction are an alkaline metal hydroxide and hydrogen gas. The word equation for the reaction of any alkali metal with water is as follows:
The reactivity of alkali metals can be proved by measuring the time they take to react completely with water. Here is a list of observations you will see with small volumes of each metal.
- Lithium fizzes on the surface of water to produce a weak bubble stream and takes the longest time to react completely out of all the alkali metals.
- Sodium fizzes on the surface of water more vigorously to produce a stronger stream of bubbles and sometimes burns with a yellow-orange flame. It takes less time to react completely than lithium.
- Potassium fizzes very strongly and burns with a lilac flame on the surface of water, and completely reacts very quickly. Explosions are often seen when potassium is reacted with water.
- Rubidium, caesium and francium explode on the surface of water in a very fast and violent reaction.