How many neutrons are in an atom of nickel with a mass number of 57?
Answer: An atom of nickel with a mass number 57 contains 29 neutrons.
Explanation: The mass number of an atom is the sum of its protons and neutrons. In the case of nickel (Ni), which has an atomic number of 28, the mass number is 57. To find the number of neutrons, subtract the atomic number (protons) from the mass number: 57 – 28 = 29 neutrons.