Arrange the following in the order of increasing reactivity towards $$\mathrm{SN}_{\mathrm{2}}$$ reactions.
$$\begin{array}{ll} \left(\mathrm{CH}_3\right)_3 \mathrm{CCH}_2 \mathrm{Br}(\mathrm{P}) ; & \\\mathrm{CH}_3\left(\mathrm{CH}_2\right)_3 \mathrm{Br}(\mathrm{Q}) ; &\\ \mathrm{CH}_3 \mathrm{CH}_2-\mathrm{CH}\left(\mathrm{CH}_3\right)-\mathrm{CH}_2 \mathrm{Br}(\mathrm{R}) ; & \\\left(\mathrm{CH}_3\right)_2 \mathrm{CHCH}_2 \mathrm{CH}_2 \mathrm{Br}(\mathrm{S}) \end{array}$$
When 0.1 mole of $$\mathrm{MnO}_4{ }^{2-}$$ is oxidised, the quantity of electricity required to completely oxidise $$\mathrm{MnO}_4{ }^{2-}$$ to $$\mathrm{MnO}_4^{-}$$ is
Choose the incorrect statement from the following.
The correct sequence of filling of electrons in $$n=6$$ is: