Final answer:
Nonmetals gain electrons to become negatively charged ions, anions, with the goal of achieving a stable electron configuration similar to noble gases, leading to a complete valence shell with eight electrons.
Step-by-step explanation:
Nonmetals gain electrons to become negatively charged ions known as anions. This process typically occurs to emulate the electron configuration of noble gases, creating stability in the atom by having a complete valence shell. Most nonmetals seek to achieve an octet, meaning eight electrons in their outermost shell, following the rule of the Periodic Table's noble gases, which are known for their stability due to having complete valence shells.
For instance, elements in Group 17 (halogens) have seven valence electrons and tend to gain one electron to form anions with a −1 charge. Similarly, elements in Group 16 (oxygen group) gain two electrons to form −2 charged anions, while those in Group 15 gain three electrons to form −3 charged anions. This gain of electrons results in a negative charge because the number of negatively charged electrons exceeds the number of positively charged protons in the atom.