The noble-gas configuration describes an outer main energy level that is occupied by how many electrons in most cases?

• A. Eight electrons
• B. Six electrons
• C. Ten electrons
• D. Two electrons

Answer: (A)

The concept here is the octet idea: atoms tend to arrange their electrons so the outermost (valence) shell is filled like a noble gas. In most cases, that outer main energy level holds eight electrons—two in the s subshell plus six in the p subshell (s2 p6). This gives a stable, low-energy configuration and explains why atoms gain, lose, or share electrons to reach eight in their valence shell. There are small exceptions: hydrogen and helium only fill their first shell with two electrons, and some heavier elements can have more than eight in their valence shell when they use d orbitals (expanded octet), but for the typical main-group scenario, eight is the goal.