In SnCl3, tin (Sn) exhibits an oxidation state of +3. This is because tin has lost three valence electrons to form three covalent bonds with the three chlorine (Cl) atoms. The oxidation state of tin can be determined by considering the electronegativity difference between tin and chlorine. Chlorine is more electronegative than tin, so the electrons in the Sn-Cl bonds are pulled towards the chlorine atoms, resulting in a partial positive charge on the tin atom. This partial positive charge corresponds to an oxidation state of +3 for tin in SnCl3.