Halogen atoms are more electronegative than carbon, therefore,
carbon-halogen bond of alkyl halide is polarised; the carbon atom bears
a partial positive charge whereas the halogen atom bears a partial
negative charge As we go down the group in the periodic table, the size of halogen
atom increases Fluorine atom is the smallest and iodine atom is the
largest Consequently the carbon-halogen bond length also increases
from C—F to C—I