Iodine has seven valence electrons. In ICl5, iodine forms five bonds with five chlorine atoms. This means that iodine uses five of its valence electrons to form the bonds. The remaining two valence electrons are not involved in bonding and are called lone pairs.

The molecular geometry of ICl5 is a square pyramid. The iodine atom is at the center of the pyramid and the five chlorine atoms are at the corners. The lone pairs of electrons occupy the two positions above and below the pyramid.

The sp3d2 hybridization of iodine explains the molecular geometry of ICl5. The s orbital and three p orbitals of iodine hybridize to form four sp3 hybrid orbitals. The two d orbitals of iodine also participate in hybridization to form two sp3d2 hybrid orbitals. The four sp3 hybrid orbitals are used to form the bonds with the five chlorine atoms. The two sp3d2 hybrid orbitals are used to hold the lone pairs of electrons.