Here's how to determine the charge of a fluorine atom's nucleus:

* Atomic Number: Fluorine has an atomic number of 9. This means it has 9 protons in its nucleus.

* Protons and Charge: Protons carry a positive charge.

* Neutrality: In a neutral atom, the number of protons (positive charge) is balanced by the number of electrons (negative charge).

Therefore, the nucleus of a fluorine atom has a charge of +9.