A neutral atom is one that has no net charge. In other words, the number of positive charges cancels out with the number of negative charges, so the number of protons equals the number of electrons. Uranium has 92 protons, which means it has a total positive charge of +92. To have a neutral charge, the atom MUST have 92 electrons, as that is a negative charge of -92, and the net charge is ultimately (protons + electrons) = ([+92] + [-92]) = 0.
