Final answer:
The provided electron configurations are incorrect because they violate the Pauli Exclusion Principle, which states a maximum of two electrons can occupy each orbital, and the Aufbau Principle, which requires electrons to fill orbitals in order of increasing energy and in a specific sequence.
Step-by-step explanation:
The electron configurations provided are incorrect based on the Pauli Exclusion Principle and the Aufbau Principle. For (a) 1s⁵ 2s³, this is incorrect because according to the Pauli Exclusion Principle, a maximum of two electrons can occupy the 1s subshell, and they must have opposite spins. Similarly, the 2s subshell can only hold a maximum of two electrons, not three. For (b) 1s⁸ 2s⁵, this is also incorrect because the 1s subshell can only accommodate two electrons, and the 2s subshell again can hold only two electrons, following the same principle.
The Aufbau Principle dictates that electrons will occupy the lowest-energy orbitals first, filling them to capacity before moving on to higher energy levels. For instance, after the 1s is full, electrons should fill the 2s and then the 2p orbitals, and so on, in sequence. These configurations disregard the proper filling order prescribed by this principle. Both provided electron configurations fail to follow these essential rules for determining correct electron arrangements in atoms.