Final answer:
Atoms of nonmetal elements gain or lose electrons to form ions. When atoms of group 17 gain one electron, they form anions with a 1- charge. Ionic bonds are formed between oppositely charged ions, and covalent bonds form when electrons are shared between atoms.
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.
Ionic and covalent bonds are strong bonds formed between two atoms. These bonds hold atoms together in a relatively stable state. Ionic bonds are formed between two oppositely charged ions (an anion and a cation). Because positive and negative charges attract, these ions are held together much like two oppositely charged magnets would stick together. Covalent bonds form when electrons are shared between two atoms. Each atom shares one of their electrons, which then orbits the nuclei of both.