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

Which of the following compounds contain polyatomic ions?
$NaOH, NaCl, Na_{2}O, NaNO_{3}$

$(a)$ Calculate the number of moles in $112 \, g$ of iron.
$(b)$ Calculate the mass of $0.5$ mole of sugar $(C_{12}H_{22}O_{11})$.
$(c)$ Calculate the number of atoms in $8 \, g$ of oxygen $(O_2)$ molecules.
(Atomic mass of $Fe = 56 \, u, C = 12 \, u, H = 1 \, u, O = 16 \, u, N_A = 6.022 \times 10^{23} \, mol^{-1}$)

Find the total number of atoms present in one $SO_{4}^{2-}$ ion.

Compute the difference in masses of one mole each of aluminium atoms and one mole of its ions. (Mass of an electron is $9.1 \times 10^{-28} \,g$). Which one is heavier (in $,g$)?

The difference in the mass of $100 \, mol$ each of sodium atoms and sodium ions is $5.48002 \, g$. Compute the mass of an electron.