One metal atom in the sample contains 115 neutrons.
The number of neutrons in an atom can be determined by subtracting the number of protons from the mass number. In this case, the metallic sample has 77 protons and a mass number of 192.
To find the number of neutrons, subtract the number of protons from the mass number:
192 (mass number) - 77 (protons) = 115 neutrons
Therefore, one metal atom in the sample contains 115 neutrons. Neutrons are subatomic particles that have no charge and contribute to the mass of an atom. In this case, the metal atom has 77 protons, 77 electrons, and 115 neutrons.