The atomic number of an atom represents the number of protons in its nucleus. In a neutral atom, the atomic number also corresponds to the number of electrons orbiting the nucleus.
Given that the atom in question has a mass number of 25 and 12 neutrons, we can determine the atomic number as follows:
Mass number (A) = Number of protons (atomic number, Z) + Number of neutrons
Therefore, in this case:
25 = Z + 12
Solving for Z, we subtract 12 from both sides:
Z = 25 - 12 Z = 13
Hence, the atomic number of the atom is 13.