What is the mass of one mole of oxygen atoms (in $g$)?

Define the term mole.

Mention the name given to the number of $6.022 \times 10^{23}$ particles.

State whether the following statement is true or false:
Atomic radius is measured in nanometres. $1 \, m = 10^9 \, nm$.

Raunak took $5 \, mol$ of carbon atoms in a container and Krish also took $5 \, mol$ of sodium atoms in another container of the same weight. $(a)$ Whose container is heavier? $(b)$ Whose container has a greater number of atoms?

If bromine atom is available in the form of,say,two isotopes $_{35}^{79}Br$ $(49.7 \%)$ and $_{35}^{81}Br$ $(50.3 \%),$ calculate the average atomic mass of bromine atom. (in $,u$)