The particle that has no charge and affects the mass of the atom is called a neutron. Neutrons are subatomic particles found in the nucleus of an atom, along with protons. Protons have a positive charge, electrons have a negative charge, but neutrons are electrically neutral, meaning they have no charge. However, they do contribute to the mass of an atom because they have a similar mass to protons. The number of neutrons in an atom can vary, leading to different isotopes of an element with the same number of protons but different numbers of neutrons.