In a platinum atom, there are 78 protons, 117 neutrons, and 78 electrons.
To break this down: the number of protons, which is equal to the atomic number of platinum, is 78. This means that every platinum atom has 78 positively charged particles in its nucleus. The neutrons in a platinum atom, which are neutral and also found in the nucleus, can vary slightly in number across different isotopes, but the most common isotope has 117 neutrons. Finally, the electrons, which are negatively charged and orbit around the nucleus, also number 78, balancing the positive charge of the protons. Therefore, a neutral platinum atom maintains an equal number of protons and electrons, resulting in no overall charge.