The colour of the X2 molecules of group 17 elements changes gradually from yellow to violet down the group. This is due to

IF Consider, X2 as F2→F2→ MoT config is σ/s2σ∗/s2σ2s2σ∗2s2σ∗2pz2π2px2=π2py2π∗2px2=π∗2py2→ HOMO σ∗2pz0→ LuMo Þ if gap between HOMO & LUMO Due to absorbed energy decreasesÞ complimentary colour is seenÞ light energy is seenÞ both ‘B’ & ‘C’ are thus applicable