Sodium (Na) is in Group 1 (also known as Alkali Metals) of the periodic table. Elements in the same group have the same number of valence electrons (outer electrons).

Therefore, the other elements that contain the same number of outer electrons as sodium are:

* Lithium (Li)

* Potassium (K)

* Rubidium (Rb)

* Cesium (Cs)

* Francium (Fr)

All these elements have one valence electron.