Question

What property of the atom changes when a neutron is added?

Answer 1

Here is your answer

Adding or removing neutrons from the nucleus are how isotopes are created. Protons carry a positive electrical charge and they alone determine the charge of the nucleus. Adding or removing protons from the nucleus changes the charge of the nucleus and changes that atom's atomic number.

Answer 2

The mass number of the element changes.

Mass number =atomic number(number of protons)+number of neutrons