One of the amazing things about the periodic table is that it shows you patterns in the elements – for example, all the group 1 metals react similarly when exposed to water. There are some very good reasons for these reactions to do with how the electrons line up in the atoms. Here we will be looking at Group 1 on the periodic table, and some of the fascinating properties that they have.
Group One elements in the periodic table are called the alkali metals. They are lithium, sodium, potassium, caesium and rubidium. Can you find them on a periodic table? They are all called group 1 elements because they all have just one electron in their outer shell.
They all react vigorously with air and water, so they must be stored in oil to stop air or water getting to them – it could cause an explosion. Don’t believe me? Take a look at this video of people putting the group 1 metals into water.
As you could see, sodium is more reactive than lithium and potassium is more reactive than sodium. You can tell, because potassium reacts extremely vigorously and quickly with water, whereas lithium less quickly and vigorously, with sodium somewhere in the middle of the reactivity series. As for caesium and rubidium - their reaction is.... explosive! So, you might have noticed by now that as you go down the periodic table you are increasing the reactiveness of the elements.
“But why are they called the alkali metals” I hear you cry from the rooftops. Well- fear not, the answer is here! Here is the general chemical equation, what do you notice about the second side?
metal + water metal hydroxide + hydrogen
Well, any time something is called a hydroxide, it is an alkali – so when the group 1 metals react with water, they form an alkali and hydrogen. Hence the term alkali metal.
So, if we where reacting lithium with water, it would look like this
Lithium + water lithium hydroxide + hydrogen.
And if we were to use potassium instead, it would look like this:
potassium + water potassium hydroxide + hydrogen.
Get the picture?
There are other patterns that you need to remember as well – take a look at them:
|Metal||Softness||Colour||Reaction with oxygen||Reaction with chlorine|
|Lithium (Li)||Hard to cut with a knife.||Grey colour, sliver when cut.||Makes Li<sub>2</sub>O (Lithium oxide)||Makes LiCl (Lithium chloride)|
|Sodium (Na)||Softer, easy to cut with a knife||White colour, sliver when cut.||Makes Na<sub>2</sub>O (Sodium oxide)||Makes NaCl (Sodium chloride)|
|Potassium (K)||Very soft - can be squeezed in tweezers.||Grey, silver when cut.||Makes K<sub>2</sub>O (Potassium oxide)||Makes KCl (Potassium chloride)|