Final answer:
Atoms of nonmetal elements generally gain electrons to form ions. Group 17 elements gain one electron to form anions with a 1- charge, while group 16 elements gain two electrons to form ions with a 2- charge.
Step-by-step explanation:
When atoms of nonmetal elements form ions, they generally gain enough electrons to give them the same number of electrons as an atom of the next noble gas in the periodic table. Atoms of group 17 gain one electron and form anions with a 1– charge; atoms of group 16 gain two electrons and form ions with a 2- charge, and so on. For example, the neutral bromine atom, with 35 protons and 35 electrons, can gain one electron to provide it with 36 electrons. This results in an anion with 35 protons, 36 electrons, and a 1- charge. It has the same number of electrons as atoms of the next noble gas, krypton, and is symbolized Brˇ.