Question

which orbital diagram shows a violation of the aufbau principle? a) 1s 2s 2p b) 1s 2s 2p c) 1s 2s 2p d) 1s 2s 2p a b c d

Explanation:

The Aufbau Principle states that electrons fill lower - energy orbitals before higher - energy orbitals. The order of filling is \(1s<2s < 2p\). Each orbital can hold a maximum of 2 electrons with opposite spins. In option A, the \(2s\) orbital (which can hold 2 electrons) is not completely filled (it has 2 unpaired electrons instead of a pair) before electrons start to enter the \(2p\) orbital. This is a violation of the Aufbau Principle. In option B, the \(2p\) orbital filling violates Hund's Rule (electrons should occupy degenerate orbitals singly before pairing), but not the Aufbau Principle. In option C, the \(2s\) orbital is not filled (only 1 electron) before \(2p\) (empty), which is wrong but not a violation of Aufbau as \(2s\) is lower energy than \(2p\) and should be filled first. However, the main violation is in A. In option D, the filling order \(1s\) (filled), \(2s\) (filled), then \(2p\) (starting to fill) follows the Aufbau Principle.

Answer:

A.