When a sodium atom loses a valence electron, it becomes a charged particle called an ion.

More specifically, it becomes a positive ion, also known as a cation.

Here's why:

* Sodium (Na) has one valence electron in its outermost shell.

* Losing this electron makes the atom have more protons (positive charge) than electrons (negative charge), resulting in a net positive charge.

* This positively charged sodium atom is now called a sodium ion (Na+).