The negatively charged particle outside the nucleus of an atom is an electron.

Here's why:

* Atomic Structure: Atoms are composed of a central nucleus containing positively charged protons and neutral neutrons. Surrounding the nucleus is a cloud of negatively charged electrons.

* Charge Balance: Atoms are electrically neutral, meaning they have an equal number of protons (positive charges) and electrons (negative charges).

* Electron Properties: Electrons are much smaller than protons and neutrons and are constantly moving around the nucleus in a complex pattern.

Let me know if you'd like to learn more about electrons or atomic structure!