In aniline, the lone pair over nitrogen atom is in conjugation with the $\mathrm{\pi }$-electrons of the benzene ring and it takes part in resonance. That is why availabiity of lone pair is not as that as in ammonia. Thus, aniline is less basic than ammonia.

On moving in the lanthanoid series from left to right successive electrons enter into ante penultimate 4f-subshell which imparts very poor shielding effect (due to its diffused nature), hence effective nuclear charge gradually increases with increase in atomic number. That is why shrinkage is observed on moving through lanthanide series, this is known as lanthanide contraction.

Nitrobenzene is reduced using Zn and NH₄Cl in alcohol medium.

The N-phenyl hydroxylamine when reacts with Tollen's reagent gives bright silver miror.

For B₂ (10$\overline{\mathrm{e}}$) the MO configuration is (σ1s)² (σ*1s)² (σ2s)² (σ*2s)² ($\mathrm{\pi }$2p${}_{\mathrm{x}}^1$ = $\mathrm{\pi }$2p${}_{\mathrm{y}}^1$)

Due to presence of unpaired electron $\left\{\mathrm{\pi }2{\mathrm{p}}_{\mathrm{x}}^1 = \mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}^1\right\}$ it shows paramagnetism.

C₂(12$\overline{\mathrm{e}}$) the MO configuration is (σ1s)² (σ*1s)² (σ2s)² ($\mathrm{\pi }$2p${}_{\mathrm{x}}^2$ = $\mathrm{\pi }$2p${}_{\mathrm{y}}^2$)

No unpaired electrons are there in C₂ $\left\{\mathrm{\pi }2{\mathrm{p}}_{\mathrm{x}}^2 = \mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}^2\right\}$, hence it shows diamagnetism.

The ratio of the rate of diffusion of oxygen to the rate of diffusion of hydrogen at constant temperatre and pressure can be calculated as

r ∝ $\frac{1}{\mathrm{m}}$

$$\begin{gathered} \frac{{\mathrm{r}}_{{\mathrm{O}}_2}}{{\mathrm{r}}_{{\mathrm{H}}_2}} = \sqrt{\frac{{\mathrm{M}}_{{\mathrm{H}}_2}}{{\mathrm{M}}_{{\mathrm{O}}_2}}} \\ \frac{{\mathrm{r}}_{{\mathrm{O}}_2}}{{\mathrm{r}}_{{\mathrm{H}}_2}} = \sqrt{\frac{2}{32}} = \frac{1}{4} \end{gathered}$$