Reactivity trends in Group 1

Group 1 metals become more reactive down the group. Lithium is less reactive than sodium, and sodium is less reactive than potassium.

Each Group 1 atom has one electron in its outer shell. When a Group 1 metal reacts, its atoms lose this outer electron. The more easily an atom loses the electron, the more readily the metal reacts.

Atoms lower down Group 1 are larger, so their outer electron is farther from the nucleus. The attraction between the nucleus and this electron is weaker, so the electron is more easily lost. This makes the metals more reactive down the group.

The trend can be used to make predictions: an alkali metal lower in Group 1 is likely to react more readily than one above it.

Group 1 electron structure and chemical properties

The elements in Group 1 are called the alkali metals. Each of their atoms has one electron in its outer shell. Although their atoms have different numbers of occupied shells, this shared outer-electron structure gives them similar chemical properties.

A Group 1 atom can relatively easily lose its single outer-shell electron during a reaction. The resulting ion has one more proton than electrons, so it has a charge of +1. For example, a sodium atom, $$\ce{Na}$$, forms a sodium ion, $$\ce{Na+}$$, by losing one electron.

Because all Group 1 atoms can lose one outer electron in this way, they form ions with the same charge and take part in similar types of chemical reactions. Their shared chemistry is therefore closely linked to their single outer-shell electron.