Chemistry - Half Equations Question. Is it possible?

well these reactions aren't actually happening in the ion form. Sn4+ ion is never present but Sn atom is in +4 oxidation state. the reaction denotes that the sn has moved from the +4 oxidation state to neutral state. Sn4+ ion was never present as it always had some part of the electron cloud within its range. this is more of a notation. so your teacher is right.