The atomic number of an element represents the number of protons in the nucleus of its atom. In this case, the atomic number is given as 13. Therefore, the atom has 13 protons.
Since the atom is neutral, it means it has an equal number of electrons as protons. So the atom also has 13 electrons.
The mass number represents the total number of protons and neutrons in the atom. In this case, the mass number is given as 45.
To find the number of neutrons, subtract the atomic number (protons) from the mass number:
Number of neutrons = Mass number - Atomic number = 45 - 13 = 32.
Therefore, the atom with an atomic number of 13 and a mass number of 45 has 13 protons, 13 electrons, and 32 neutrons.