Who proposed the laws of chemical combination?

Classify each of the following on the basis of their atomicity:
$(a) F_2$
$(b) NO_2$
$(c) N_2O$
$(d) C_2H_6$
$(e) P_4$
$(f) H_2O_2$
$(g) P_4O_{10}$
$(h) O_3$
$(i) HCl$
$(j) CH_4$
$(k) He$
$(l) Ag$

Write the chemical formulae of the compounds formed by the following ions:
$(a)$ $Mg^{2+}$ and $S^{2-}$
$(b)$ $Cu^{2+}$ and $OH^-$
$(c)$ $Al^{3+}$ and $Br^-$
Name the compounds formed in each case.

The relative atomic mass of an oxygen atom is $16$. Explain its meaning.

Which of the following correctly represents $360 \,g$ of water?

Mass of one atom of oxygen is