91Ó°ÊÓ

We have to Identify the group or period number which contains$\mathrm{C}$,$\mathrm{N}$and$\mathrm{O}$.

• Analysing the periods and groups of modern periodic table.
• According to the modern periodic table period $2$contains $\mathrm{C}$,$\mathrm{N}$and $\mathrm{O}$

We have to Identify the group or period number which begins with helium.

• Analysing the periods and groups of modern periodic table.
• According to the modern periodic table Group $8A\left(18\right)$begins with helium.

We have to Identify the group or period number which contains the alkali metals.

• Analysing the periods and groups of modern periodic table.
• According to the modern periodic table Group $1A\left(1\right)$contains alkali metals.

We have to Identify the group or period number which ends with neon.

• Analysing the periods and groups of modern periodic table.
• According to the modern periodic table Period $2$ends with Neon.