Write down the electron distribution of chlorine atom. How many electrons are there in the $L$ shell? (Atomic number of chlorine is $17$).

Define valency by taking examples of silicon and oxygen.

Which of the $Na^+$ and $He$ has completely filled $K$ and $L$ shells? Give a reason to support your answer.

$A, B$ and $C$ are three metals with atomic numbers $4, 11$ and $13$ respectively. Arrange the metals in the increasing order of their valency.

$A$ helium atom has $2$ electrons in its valence shell,but its valency is not $2$. Explain.

$(a)$ Explain Bohr$-$Bury rules for the distribution of electrons into different shells.
$(b)$ Write the electronic configuration of an atom of sulphur. Also,draw a schematic diagram of its atom showing the distribution of electrons in its shells.