Sodium (Na) is in group 1 of the periodic table, meaning it has one outer electron. Other elements in group 1 also have one outer electron. These are:

* Lithium (Li)

* Potassium (K)

* Rubidium (Rb)

* Cesium (Cs)

* Francium (Fr)

These elements are known as the alkali metals and share similar chemical properties due to their single outer electron.