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Sulfur, phosphorus, silicon, and chlorine are common examples of elements that form an expanded octet. Phosphorus pentachloride (PCl5) and sulfur hexafluoride (SF6) are examples of molecules that deviate from the octet rule by having more than 8 electrons around the central atom.

Sulfur can follow the octet rule as in the molecule SF2. Each atom is surrounded by eight electrons. It is possible to excite the sulfur atom sufficiently to push valence atoms into the d orbital to allow molecules such as SF4 and SF6. The sulfur atom in SF4 has 10 valence electrons and 12 valence electrons in SF6.

Sulfur can make use of its 2 unpaired electrons to form 2 covalent bonds plus the 4 electrons from its 2 lone pairs to give a total of 8 electrons. Hence sulfur obeys octet rule in this case. But sulfur can unpair its electrons and promote one of its electrons (highlighted in green) to an empty 3d orbital.

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Most nonmetal atoms, including sulfur, tend to form anions, which means they gain, not lose electrons, to fill its octet.

Halogens always form anions, alkali metals and alkaline earth metals always form cations. Most other metals form cations (e.g. iron, silver, nickel), whilst most other nonmetals typically form anions (e.g. oxygen, carbon, sulfur).

Sulfur is the third most abundant element in your body. It is present in methionine and cysteine, which are two of the amino acids you use to make proteins. Both of these amino acids are present in your skin, hair, and nails where they help to make these tissues strong and flexible.