ine ▁is ▁green ish - yellow , ▁and ▁b rom ine ▁is ▁a ▁re dd ish - b rown ▁vol atile ▁liquid ▁that ▁mel ts ▁at ▁− 7 . 2   ° C ▁and ▁bo ils ▁at ▁ 5 8 . 8   ° C . ▁( I od ine ▁is ▁a ▁sh iny ▁black ▁solid .) ▁This ▁tr end ▁occurs ▁because ▁the ▁w avel ength s ▁of ▁visible ▁light ▁absor bed ▁by ▁the ▁hal og ens ▁increase ▁down ▁the ▁group . ▁Specifically , ▁the ▁colour ▁of ▁a ▁hal ogen , ▁such ▁as ▁b rom ine , ▁results ▁from ▁the ▁electron ▁transition ▁between ▁the ▁highest ▁occupied ▁ant ib ond ing ▁ π g ▁mole cular ▁orb ital ▁and ▁the ▁lowest ▁vac ant ▁ant ib ond ing ▁ σ u ▁mole cular ▁orb ital . ▁The ▁colour ▁f ades ▁at ▁low ▁temper atures , ▁so ▁that ▁solid ▁b rom ine ▁at ▁− 1 9 5   ° C ▁is ▁pale ▁yellow . ▁ ▁Like ▁solid ▁ch lor ine ▁and ▁i od ine , ▁solid ▁b rom ine ▁cry st all ises ▁in ▁the ▁orth or h omb ic ▁cry stal ▁system , ▁in ▁a ▁layer ed ▁lattice ▁of ▁Br 2 ▁mole cules . ▁The ▁Br – Br ▁distance ▁is ▁ 2 2 7   pm ▁( close ▁to ▁the ▁g ase ous ▁Br – Br ▁distance ▁of ▁ 2 2 8   pm ) ▁and ▁the ▁Br · · · Br ▁distance ▁between ▁mole cules ▁is ▁ 3 3 1   pm ▁within ▁a