Final answer:
Option a) [He]2s²2px²2py²2pz' violates Hund's rule because it shows the 2pz orbital being doubly occupied before the 2py orbital is singly occupied, which is not in accordance with Hund's rule of maximum multiplicity.
Step-by-step explanation:
The question posed is which electron configuration violates Hund's rule. Hund's rule states that every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin. Given the configurations:
- a) [He]2s²2px²2py²2pz'
- b) [He]2s²2px²2py²2pz²
- c) [He]2s²2px²2py²2pz²
- d) [He]2s²2px²2py²2pz'
- e) [He]2s²2px²2py'2pz'
The correct one that violates Hund's rule is option a) because it shows a pair of electrons in the 2pz orbital before the 2py orbital has been singly occupied, which contradicts Hund's principle of maximum multiplicity.