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

$\mathrm{Na},\mathrm{Mg},\mathrm{Al}$ 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. 

For the following pair, which one is larger in size?

$\mathrm{Na} \mathrm{and} {\mathrm{Na}}^{+}$.

Elements have been arranged in the following sequence on the basis of their increasing atomic masses.

$\mathrm{F}, \mathrm{Na}, \mathrm{Mg}, \mathrm{Al}, \mathrm{Si}, \mathrm{P}, \mathrm{S}, \mathrm{Cl}, \mathrm{Ar}, \mathrm{K}$

The given sequence represents which law of classification of elements?

The question is concerned with the elements in period 5, Rb to Xe.

The electron distribution of some of these elements are given in the following list.

Element A    2 + 8 + 18 + 8 + 2

Element B    2 + 8 + 18 + 18 + 8

Element C   2 + 8 + 18 + 18 + 5

Element D    2 + 8 + 18 + 18 + 6

Element E    2 + 8 + 18 +18 + 4

Element F    2 + 8 + 18 +18 + 7

Identify element C.