An atom has three subatomic particles: (1) neutrons, (2) protons, and (3) electrons. Both neutron and proton stay inside the atom's nucleus and comprised mainly the mass of the atom. The electron however is a negatively charged subatomic particle and stays outside of the nucleus. In a neutral atom, the number of protons and electrons should be equal. However, if the atom is negatively charged, this means it contains more electrons than protons.
If the ion is positively charged, this means that it contains more proton than electrons.
If an atom loses one if its electrons then, it becomes negatively charged. Since, only one electron is lost then the answer to this item is the second choice, +1.
