Final answer:
Sulfur (S) is an element in Group 16 that has the same number of outer-shell (valence) electrons as oxygen, which is six. Like oxygen, sulfur can form double bonds to satisfy the octet rule.
Step-by-step explanation:
An element that has the same number of outer-shell (valence) electrons as oxygen would be another element in Group 16 of the periodic table. Oxygen has six valence electrons as it is a Group 6A (or Group 16 using the IUPAC nomenclature) element. The elements in Group 16 are called chalcogens and include oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po). Except for oxygen, all these elements will similarly have six valence electrons.
Oxygen typically forms a double covalent bond in oxygen gas (O=O) where two oxygen atoms share two pairs of electrons to follow the octet rule, each achieving stability by having eight electrons in their valence shell.
When comparing to oxygen, sulfur (S) is the element that most commonly appears in compounds and thereby is frequently mentioned in the context of having six valence electrons like oxygen. Similar to oxygen, sulfur can also form multiple bonds and share electrons to follow the octet rule.