Draw orbit structure diagram of calcium oxide $\left(\mathrm{CaO}\right)$.

[Atomic numbers $\mathrm{Ca}=20, \mathrm{O}=8$]

Compare chlorine atom and chloride ion, with respect to their electrical state.

Give an example of covalent bond formed by:

Similar atoms.

Out of the following atomic numbers $4,8,10,15$ and $19$ which element can form the trivalent ion.

Out of the following atomic numbers $4,8,10,15$ and $19$ find out the element with $4$ shells.

Out of the given atomic numbers $4,8,10,15$ and $19$ which of the given element have $6$ valence electrons.

Match the atomic numbers $4,8,10,15$ and $19$ with each of the following:

Element which does not form ion.