Here's how to determine the number of electrons in a theoretical atom of Uuo-291:

* Uuo is the symbol for the element Ununoctium, which has an atomic number of 118. This means a neutral Ununoctium atom has 118 protons.

* 291 is the mass number, indicating the total number of protons and neutrons in the atom's nucleus.

* Neutral atoms have an equal number of protons and electrons.

Therefore, a neutral Uuo-291 atom would have 118 electrons.