Statement I: The oxidation states of a transition element normally differ from each other by unity, for example V(II), V(III), V(IV) and V(V).
Statement II: Early in the first transition series, titanium(III) is more stable than titanium(IV).
In the light of the above statements, choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Only Statement I is correct.
Transition elements show variable oxidation states because both their ns and (n−1)d electrons can take part in bonding, and the d orbitals can be filled to different extents.
Statement I: The oxidation states of a transition element normally differ from each other by unity, for example V(II), V(III), V(IV) and V(V). — True. The d electrons can be lost one at a time, so the states differ by one. In non-transition elements the oxidation states normally differ by two.
Statement II: Early in the first transition series, titanium(III) is more stable than titanium(IV). — False. Titanium (3d2 4s2) has few electrons to lose; its most stable state uses all four of them, so titanium(IV) is more stable than Ti(III) or Ti(II), as in TiO2.
NCERT (2026-27 edition):
4.3.4 Oxidation States – “…Thus, early in the series scandium(II) is virtually unknown and titanium (IV) is more stable than Ti(III) or Ti(II).”
“The variability of oxidation states, a characteristic of transition elements, arises out of incomplete filling of d orbitals in such a way that their oxidation states differ from each other by unity, e.g., VII, VIII, VIV, VV. This is in contrast with the variability of oxidation states of non transition elements where oxidation states normally differ by a unit of two.”