The HOMO (highest occupied molecular orbital) to LUMO (lowest unoccupied molecular orbital) electronic transition responsible for the observed colours of halogen molecules (gas) is
(a)$\pi^{*} \rightarrow \sigma^{*}$
(b)$\pi^{*} \rightarrow \pi^{*}$
(c)$\sigma \rightarrow \sigma^{*}$
(d)$\pi \rightarrow \sigma^{*}$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
Halogen colours come from the π* (HOMO) → σ* (LUMO) transition, which moves to longer wavelength down the group (F₂ yellow → I₂ violet).