The lattice site in a pure crystal cannot be occupied by electrons; because in each lattice point of a pure crystal (no impurity) there is only space for either molecule or atom or ions which are essentially joined together in straight lines and leads to a specific geometrical shape for each crystal. And they are also arranged in stoichiometric ratio which is fixed in proportion.

• But electrons can only occupy when there is a vacancy or defect in the corresponding crystal, i.e. crystal is no more in pure form it has impurities.

Hence, options (i) molecule, (ii) ion and (iv) atom are not correct because they can occupy the lattice site of a pure crystal.