(i) " Ti(IV) is more stable than Ti(III) and Ti(II)." True. Among titanium's common oxidation states (+2,+3,+4), the +4 state is generally the most stable due to the high lattice or coordination stabilization and the noble-gas-like configuration of Ti∧(4+)(3d∧0). (ii) "Among 3d-series elements ( Z=22 to 29 ), only copper has a positive reduction potential (M∧(2+)∕M )." True. Standard reduction potentials for most 3d metals (like Ti, V, Cr, Mn, Fe, Co, Ni, Zn) are negative. Copper is unique with a standard reduction potential of about +0.34 V , making it the only one in that range with a positive reduction potential for the M∧(2+)∕M couple. (iii) "Both Sc and Zn exhibit +1 oxidation state." False. Sc typically shows +3 oxidation state (it is isoelectronic with Ar when Sc∧(3+)). Instances of Sc in +1 or +2 are either extremely rare or not well-established. Zn commonly shows +2. While there are organometallic complexes where Zn can appear in unusual oxidation states, Zn(+1) is not a stable or typical oxidation state in standard inorganic chemistry contexts.
