Which group of elements in the periodic table is most likely to form compounds with an expanded octet?

• A. Elements in period 2 (such as C, N, O, F)
• B. Alkali metals (group 1)
• C. Noble gases in period 1
• D. Elements in period 3 and beyond (such as P, S, Cl)

Answer: (D)

Verified step by step guidance

1. Understand the concept of the octet rule: atoms tend to form compounds in ways that give them eight electrons in their valence shell, achieving a stable electron configuration similar to noble gases.
2. Recognize that elements in period 2 (such as C, N, O, F) are limited to an octet because they only have s and p orbitals available in their valence shell, so they cannot expand beyond 8 electrons.
3. Know that alkali metals (group 1) typically lose one electron to form +1 ions and do not form expanded octets because they have only one valence electron.
4. Note that noble gases in period 1 (which is just hydrogen and helium) have very limited valence shells and do not form expanded octets or many compounds.
5. Identify that elements in period 3 and beyond (such as P, S, Cl) have access to d orbitals in their valence shell, allowing them to accommodate more than 8 electrons and thus form compounds with expanded octets.