order of overlap of atomic orbitals from highest extent of overlap to lowest is, I2 > IBr > ICl > IF Because, I2-is homo diatomic molecule and having good overlapping between the atomic orbitals of two iodine atoms. IBr-is a hetero di-atomic molecule and having almost good overlapping between the atomic orbitals of iodine and bromine atoms even though these two atoms belongs to different periods. ICl-is a hetero di-atomic molecule and having moderate overlapping between the atomic orbitals of iodine and chlorine atoms.Because, these two atoms belongs to different periods and size different is more. IF-is a hetero di-atomic molecule and having poor overlapping between the atomic orbitals of iodine and fluorine atoms.Because, these two atoms belongs to different periods and size different is too more. Solution order of overlap of atomic orbitals from highest extent of overlap to lowest is, I2 > IBr > ICl > IF Because, I2-is homo diatomic molecule and having good overlapping between the atomic orbitals of two iodine atoms. IBr-is a hetero di-atomic molecule and having almost good overlapping between the atomic orbitals of iodine and bromine atoms even though these two atoms belongs to different periods. ICl-is a hetero di-atomic molecule and having moderate overlapping between the atomic orbitals of iodine and chlorine atoms.Because, these two atoms belongs to different periods and size different is more. IF-is a hetero di-atomic molecule and having poor overlapping between the atomic orbitals of iodine and fluorine atoms.Because, these two atoms belongs to different periods and size different is too more..