The correct answer is (4) an electron.
In a crystal lattice, which is a three-dimensional arrangement of repeating units called unit cells, various types of particles can occupy lattice points. These particles can include atoms, molecules, and ions, but electrons are not found occupying lattice points in the same way.
1. Atoms: In many crystalline materials, particularly elemental solids, individual atoms occupy the lattice points. Each lattice point represents the position of a single atom of the substance. For example, in a crystal of sodium chloride (\(NaCl\)), sodium (\(Na\)) ions occupy some lattice points, and chloride (\(Cl\)) ions occupy others.
2. Molecules: Some crystalline substances consist of molecules that are relatively large compared to individual atoms. In these cases, the molecules themselves occupy the lattice points. An example is ice (\(H_2O\)), where each lattice point is occupied by a water molecule (\(H_2O\)).
3. Ions: Ionic compounds like sodium chloride (\(NaCl\)) consist of positively charged ions (cations) and negatively charged ions (anions). In these crystals, cations and anions occupy alternate lattice points in a repeating pattern. The crystal structure is determined by the arrangement of these ions.
4. Electrons: Electrons are not found occupying lattice points in the same manner as atoms, molecules, or ions. Electrons are subatomic particles that participate in the electron cloud or electron cloud distribution of the crystal. In a solid, electrons are shared among the atoms or ions in a way that forms electron bands, energy levels, or electron clouds that extend throughout the crystal structure. This behavior is described by quantum mechanics, and it's fundamentally different from how atoms, molecules, or ions are arranged at specific lattice points.
In summary, lattice points in a pure crystal can be occupied by atoms, molecules, or ions, depending on the type of substance. However, electrons are not localized to specific lattice points but rather participate in the electron distribution or band structure of the crystal. |
