Which term describes the general distribution of electrons among the orbitals and subshells of an atom?

• A. Noble-gas configuration
• B. Electron configuration
• C. Aufbau principle
• D. Chemical bonding

Answer: (B)

Electron configuration describes how electrons are distributed among an atom's orbitals and subshells. It tells you which orbitals are occupied and how many electrons each contains, following the order of increasing energy and the rules that govern filling—such as the Aufbau principle, Pauli exclusion, and Hund's rule. For example, neon has a distribution written as 1s2 2s2 2p6, showing exactly how many electrons sit in each orbital. Noble-gas configuration is a shorthand way to write the same distribution by starting from a noble gas core (like [Ne] 2s2 2p6 for magnesium), not a different idea about where electrons reside. The Aufbau principle explains why electrons fill in a specific sequence, but the principle itself is about the filling order rather than the final distribution. Chemical bonding, by contrast, deals with how atoms interact and share or transfer electrons with other atoms, not the arrangement inside a single atom.