When a sodium atom loses its valence electron, it becomes a charged particle called a cation.

Here's why:

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

* Losing an electron makes the atom have more protons (positive charge) than electrons (negative charge).

* A positively charged ion is called a cation.

So, a sodium atom that has lost its valence electron becomes a sodium cation (Na+).