Flourine is Gas and Iodine is Solid

Question: Flourine is Gas and Iodine is Solid ?

Ans : Flourine and Iodine both belong to Helogens group.In halogen as we move from top to bottom number of electrons increases.Flourine is on the top in halogens and iodine is in last of halogens.Flourine has small number of electrons and Iodine has greater number of electrons (53) around its nucleus.So, unsymmetrical electronic distribution or polariziblity of Iodine is also very high.Hence strong London forces of dispersion are present among iodine molecules.Due to which iodine is soild at room temperture.