Calculate the molecular masses of $H_2$,$O_2$ and $Cl_2$.

Why is it not possible to see an atom with naked eyes?

When $3.00 \,g$ of carbon is burnt in $8.00 \,g$ of oxygen,$11.00 \,g$ of carbon dioxide is produced. What mass of carbon dioxide will be formed when $3.00 \,g$ of carbon is burnt in $50.00 \,g$ of oxygen? Which law of chemical combination will govern your answer?

How many atoms are present in a $(i)$ $H_2S$ molecule and $(ii)$ $PO_4^{3-}$ ion?

Which has more number of atoms,$100\,g$ of sodium or $100\,g$ of iron (given,atomic mass of $Na = 23\,u, Fe = 56\,u$)?

Write down the chemical formulae of:
$(i)$ Sodium oxide
$(ii)$ Aluminium chloride
$(iii)$ Sodium sulphide
$(iv)$ Magnesium hydroxide