Here's why:

* Atoms are neutral, meaning they have an equal number of protons (positive charge) and electrons (negative charge).

* Removing an electron leaves the atom with more protons than electrons, resulting in a net positive charge.

* Cations are ions (atoms with a net charge) with a positive charge.

For example, if you remove an electron from a sodium atom (Na), you get a sodium ion (Na+) which is a cation.