If Δ₀<p, then the electronic configuration of d4 species will be

CONCEPT:

Crystal Field Splitting and Weak Field Ligands

• In a coordination complex, the d-orbitals of the central metal ion split into two sets of orbitals: t_2g (lower energy) and e_g (higher energy).
• The splitting energy between these two sets of orbitals is denoted as Δ₀.
• The relative magnitude of Δ₀ compared to the pairing energy (p) determines the arrangement of electrons in the d-orbitals.
• If Δ₀ < p (weak field ligands), electrons prefer to occupy higher energy orbitals (e_g) before pairing in the lower energy orbitals (t_2g).

EXPLANATION:

• For a d⁴ configuration, if Δ₀ < p (weak field case):
  • Electrons will follow Hund's Rule, occupying each orbital singly before pairing occurs.
  • The first three electrons will occupy the lower energy t_2g orbitals.
  • The fourth electron will occupy one of the higher energy e_g orbitals.
• This results in the electronic configuration: t_2g³ e_g¹.

Therefore, the correct answer is Option 3: t_2g³ e_g¹.