You would expect elements in the same group (vertical column) of the periodic table as sodium to have similar chemical behavior. This is because elements in the same group have the same number of valence electrons, which are the electrons in the outermost shell and determine how an element bonds with other elements.

Sodium is in Group 1, also known as the alkali metals. Therefore, the elements that share similar chemical behavior with sodium are:

* Lithium (Li)

* Potassium (K)

* Rubidium (Rb)

* Cesium (Cs)

* Francium (Fr)

All of these elements are highly reactive metals, readily losing their single valence electron to form +1 ions. This makes them good conductors of heat and electricity, and they react vigorously with water to produce hydrogen gas.