Order of Lewis acid character among sulfur hexafluoride, sulfur tetrafluoride and tetrachloromethane
S is in its highest oxidation state (+6) it has no electrophilicity hence not a Lewis acid.
Also, CCl4 can't have more than 8 electrons in its outermost orbit and it can not also increase it's coordination number also so it can't behave as a Lewis acid.
SF4 can accept electrons as S isn't in its highest oxidation state.
Hence order of Lewis acid character is : SF4 &gt; CCl4 = SF6