Atoms/Molecules/Ions

1) Bromine is a molecule because it is a diatom.

2) Zinc is an atom because it is only one particle.

3)Carbon dioxide is a molecule because there is covalent bond between the C and O. CO2 has the structure of O=C=O

4)Magnesium sulphate is consists of Mg^2+ and SO4^2- ion.

5) Carbon is an atom, single particle.

6) Sulphur dioxide molecule, covalent bonding between S and O.

7) Sodium atom, single particle.

8) Potassium Sulphide, consists of K^+ and S^2-

In conclusion whenever you see something directly out of the periodic table are atoms (except the diatomic N, O, F, Cl, Br, I). If everything in the formula is non-metal, it is a molecule. If there is metal and non metal parts in the formula, it consists of positively charged metal and negatively charged non metal.