Question

What happens to a neutral nonmetal atom in order for the octet rule to be satisfied?

Answer 1

It either gains one or more electrons to form a charged monoatomic ion or share one or more pairs of electrons with another atom.

Explanation:

The nonmetal atom becomes an ion
Nonmetals can receive electrons from a complete electron transfer to form negatively-charged ions. For example, a neutral chlorine atom might gain one electron to form a chloride `"Cl"^(-)` ion:

`"Cl"color(white)(l) + color(white)(l) "e"^(-) to "Cl"^(-)`

The electron added in this process would fill the empty `3p` orbital in the chlorine atom to complete the octet.

• `"Cl"`: `1s^2 2s^2 2p^2 ul(3s^color(navy)(2) 3p^color(purple)(5)) color(white)(l) color(grey)("incomplete valence shell")`
• `"Cl"^(-)`: `1s^2 2s^2 2p^2 ul(3s^color(navy)(2) 3p^color(navy)(6)) color(white)(l) color(grey)("extra electron completes the octet")`

The nonmetal atom forms covalent bonds with other atoms
Alternatively, a nonmetal atom might share one or more pairs of electrons with another atom to achieve an octet. Atomic orbitals of the two atoms "overlap" in a way that valence electrons from one atom fill vacancies in electron orbitals of the other.

For example, a hydrogen atom joins a chlorine atom to form a hydrogen chloride molecule.

The chlorine atom has now attained an octet. (Keep in mind that it takes only two valence electrons for a hydrogen atom to achieve the electron configuration of noble gas helium `"H" "e"`, which also contains two electrons. The fact that a hydrogen atom is chemically stable with less than valence eight electrons is an exception to the octet rule).