(i) H₂S molecule (Hydrogen sulfide):
– Hydrogen sulfide (H₂S) comprises 2 atoms of hydrogen (H₂) and 1 atom of sulfur (S) per molecule.
– Thus, within one molecule of hydrogen sulfide, there are a total of 3 atoms: 2 hydrogen atoms and 1 sulfur atom.

(ii) PO₄³⁻ ion (Phosphate ion):
– The phosphate ion (PO₄³⁻) consists of 1 atom of phosphorus (P) and 4 atoms of oxygen (O₄).
– The ion carries a 3- charge, indicating the addition of three electrons, but not involving extra physical atoms.
– Consequently, in one phosphate ion, there are 1 phosphorus atom and 4 oxygen atoms, totaling 5 entities when considering the charge.

In short, a single molecule of hydrogen sulfide contains 3 atoms (2 hydrogen and 1 sulfur), while one phosphate ion consists of 5 entities, representing 1 phosphorus atom and 4 oxygen atoms along with the charge.