Give the name and electronic configuration of the halogen which is liquid is at room temperature.

Metals have a tendency to form cations. Give reason. 

$\mathrm{C}\left(6\right)$ and $\mathrm{Si}\left(14\right)$ belong to group $14$ of the Periodic Table. Write the electronic configuration and valency of these two elements. 

$\mathrm{Na},\mathrm{Mg},\mathrm{Al}$ and $\mathrm{P}$ belong to $3$rd period but are placed in the first, second, thirteenth and fifteenth groups. The number of shells occupied in $\mathrm{Mg}$ is three. What is the number of occupied shells in $\mathrm{Na},\mathrm{Al}$ and $\mathrm{P}$. Give a reason for your answer. 

Two elements $\mathrm{X}$ and $\mathrm{Y}$ belong to group $1$ and $2$ respectively in the same period of Periodic Table. Compare these elements with respect to their valencies.

Two elements $\mathrm{X}$ and $\mathrm{Y}$ belong to group $1$ and $2$ respectively in the same period of Periodic Table. Compare these elements with respect to the formula of their chlorides.

Two elements $\mathrm{X}$ and $\mathrm{Y}$ belong to group $1$ and $2$ respectively in the same period of Periodic Table. Compare these elements with respect to the formula of their sulphates.