Here's why:

* Sodium (Na) is in Group 1 of the periodic table, also known as the alkali metals.

* Alkali metals have one valence electron (electron in the outermost shell).

* To achieve a stable electron configuration, sodium readily loses its single valence electron, forming a positively charged ion (cation).

* The loss of the negative charge from the electron leaves the sodium atom with a +1 charge, resulting in the Na⁺ ion.