Based on the metallic radii provided, which transition element exhibits the highest density?

Element	Fe	Co	Ti	Cu
Metallic radii/pm	126	125	147	128

1. Fe 

2. Ti

3. Co

4. Cu

The electronic configuration of gadolinium (atomic number of 64) is:

1. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{3}5{\mathrm{d}}^{5}6{\mathrm{s}}^2$

2. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}5{\mathrm{d}}^{2}6{\mathrm{s}}^1$

3. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$

4. $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{8}5{\mathrm{d}}^{6}6{\mathrm{s}}^2$

Match Column I (Catalyst) with Column II (Process), and mark the appropriate option:

Codes:

:
Why does manganese show a maximum oxidation state of +4 in MnF₄ but reach +7 in Mn₂O₇?

Among the following, which are amphoteric oxides?

1. V₂O₅, Cr₂O₃
2. Mn₂O₇, CrO₃
3. CrO, V₂O₅
4. V₂O₅, V₂O₄

Urea reacts with water to form A, which decomposes to form B. When B is passed through ${\mathrm{Cu}}^{2+}$ (aq), a deep blue-colored solution C is formed

The formula of C is: 

1. ${\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_4\right]}^{2+}$

2. $\mathrm{Cu}{\left(\mathrm{OH}\right)}_2$

3. ${\mathrm{CuCO}}_3.\mathrm{Cu}{\left(\mathrm{OH}\right)}_2$

4. ${\mathrm{CuSO}}_4$

Colourless ion among the following is:

An element among the following that exhibits the maximum oxidation state is:

1. Cr

2. Mn

3. Fe

4. V

Match the following characteristics to the appropriate metal:  

Select the correct option :

Mn²⁺ compounds are more stable than Fe²⁺ compounds towards oxidation in their +3 state because :