Why SF4 is highly reactive and SF6 highly inert ?
In SF4, there are vacant d–orbital present as S is bonded to only 4 F atoms and hence has 1 non-bonding pair of electrons. Therefore SF4 is not stable and can react further with available non-bonding pair of electrons hence more reactive. While in SF6, there are no vacant d-orbital as the S is bonded with 6 F atoms and all the electrons are paired thus the octet of sulphur is complete making SF6 more stable and inert for further reactions.