The symbols of calcium,carbon,and copper are

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

Give one relevant reason why scientists chose $1/16$ of the mass of an atom of naturally occurring oxygen as the atomic mass unit.

Name the elements represented by the following symbols:
$(a)$ $Au$
$(b)$ $Ag$
$(c)$ $Hg$
$(d)$ $Sn$

$(a)$ Write the chemical formula of sodium sulphate.
$(b)$ Name one element each that forms a diatomic and a tetraatomic molecule.

What formed the basis for John Dalton to formulate Dalton's atomic theory?