Final answer:
The ion of platinum with a mass number of 195 and 74 electrons has 78 protons, 117 neutrons, and a 4+ charge.
Step-by-step explanation:
The number of protons in an atom determines its atomic number, which is the same as the number of electrons in a neutral atom. In this case, the ion of platinum has 74 electrons. The mass number of the ion, which is determined by the sum of protons and neutrons, is given as 195.
Since the atomic number of platinum is 78, the ion must have 78 protons. To find the number of neutrons, subtract the atomic number from the mass number: 195 - 78 = 117 neutrons.
The charge of the ion can be determined by comparing the number of protons and electrons. Since the ion has 78 protons and 74 electrons, it has a charge of 4+ (78 - 74 = 4+).