According to the Paneth-Fajans rule, the ion preferably adsorbed from a solution on the surface of a solid crystalline adsorbent is the ion, which:

Answer options

1. Is included in the crystal lattice of the adsorbent
2. Forms an easily soluble compound with one of the lattice ions
3. Is not included in the crystal lattice of the adsorbent
4. Forms a sparingly soluble compound with one of the lattice ions
5. Does not form a sparingly soluble compound with one of the lattice ions