The number of neutrons in an atom is calculated by subtracting the atomic number from the atomic mass (mass number). The atomic number equals the number of protons in the atom, and both numbers can be found on the periodic table. Mathematically, this is expressed as:
Number of neutrons=Atomic mass (mass number)−Atomic number\text{Number of neutrons}=\text{Atomic mass (mass number)}-\text{Atomic number}Number of neutrons=Atomic mass (mass number)−Atomic number
For example, if an element has an atomic mass of 16 and an atomic number of 8 (like oxygen), the number of neutrons is:
16−8=816-8=816−8=8
Note that the atomic mass used here is often rounded to the nearest whole number to represent the mass number, especially for isotopes. The number of neutrons can vary between isotopes of the same element. This method allows calculation of neutrons directly from standard periodic table information.
