5. Select the group that contains only molecules.
A Water, methane, copper chloride
B Hydrogen, sulfur, argon
C Ethane, lead, diamond, oxygen
D Bromine, fluroine, silicon dioxide, water
A is wrong since copper chloride is ionic and hence, does not occur as a molecule.
B is correct since all of these can form/exist as molecules. Sulfur can exist as a molecule (e.g. S2).
C is wrong since lead is a metal and hence does not occur as a molecule.
D is wrong since silicon dioxide is a covalent network substance. Covalent network structures do not exist as molecules but instead they occur as an infinite 3D array of atoms.
