Which one of the following ions is the most stable in an aqueous solution? 
(At. No. Ti = 22, V = 23, Cr = 24, Mn = 25)

1. \(\text{Cr}^{3 +}\)

2. \(\text V^{3 +}\)

3. \(\text{Ti}^{3 +}\)

4. \(\text{Mn}^{3 +}\)

The d-electron configurations of Cr²⁺, Mn²⁺, Fe²⁺ and Ni²⁺ and 3d⁴, 3d⁵, 3d⁶ and 3d⁸ respectively.
Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour? 
(At. No. Cr = 24, Mn = 25, Fe = 26, Ni = 28)

1. \(\left[\mathrm{Mn}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)
2. \(\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)
3. \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)
4. \(\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\)

The manganate and permanganate ions are tetrahedral, due to:

Which one of the elements with the following outer orbital configurations may exhibit the largest number of oxidation states?

1. 3d³, 4s²

2. 3d⁵, 4s¹

3. 3d⁵, 4s²

4. 3d², 4s²

Which of the following pairs has the same size?

1. $F{e}^{2+},$ $N{i}^{2+}$

2. $Z{r}^{4+},$ $T{i}^{4+}$

3. $Z{r}^{4+},$ $H{f}^{4+}$

4. $Z{n}^{2+},$ $H{f}^{4+}$

Which one of the following ions has electronic configuration [Ar] 3d⁶? 
(At. no :Mn = 25, Fe= 26, Co= 27, Ni = 28)

1. $N{i}^{3+}$

2. $M{n}^{3+}$

3. $F{e}^{3+}$

4. $C{o}^{3+}$

Which of the following ions will exhibit colour in aqueous solutions?

1. La³⁺ (Z=57)

2. Ti³⁺ (Z=22)

3. Lu³⁺ (Z=71)

4. Sc³⁺ (Z=21)

Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of:

1.  ${\mathrm{CrO}}_4^{2-}$

2.  ${\mathrm{Cr}}_2{\left({\mathrm{SO}}_3\right)}_3$

3.  ${\mathrm{CrSO}}_4$

4.  ${\mathrm{Cr}}_2{\left({\mathrm{SO}}_4\right)}_3$

1.  Fe>Mn>Co>Cr

2.  Co>Mn>Fe>Cr

3.  Cr>Mn>Co>Fe

4.  Mn>Fe>Cr>Co