Question

Which element is the most variable in properties?

Answer 1

hmm i'd say carbon because depending on what it's bound to, it's properties change drastically.

Answer 2

yeah, carbon is the right answer but i don't know on what basis you're asking this question. usually the properties of any element is decided by it's valence electrons and it's ability to gain or lose those valence electrons, so on this basis manganese (Mn) having 10 oxidation states is the most variable in properties.