Q.Classify the following solids in different categories based on the nature of intermolecular forces operating in them: Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide.

Step 1 – Basis of classification.

Solids are grouped by the nature of the forces holding their particles: ionic (electrostatic ion–ion), metallic (electron-sea), covalent network (continuous covalent bonds) and molecular (dispersion / dipole–dipole / H-bonding).

Step 2 – Assign each substance.

• Potassium sulphate ($K_2SO_4$) — ionic (cation + polyatomic anion)
• Tin ($Sn$) — metallic
• Benzene — molecular (non-polar, dispersion forces)
• Urea — molecular (polar, dipole–dipole and H-bonding)
• Ammonia ($NH_3$) — molecular (polar, hydrogen bonding)
• Water ($H_2O$) — molecular (hydrogen-bonded)
• Zinc sulphide ($ZnS$) — ionic
• Graphite — covalent (network) solid
• Rubidium ($Rb$) — metallic …

Identify each substance's bonding: salts $\to$ ionic; metals $\to$ metallic; giant covalent networks (graphite, SiC) $\to$ covalent; discrete molecules/atoms held …

• Calling graphite or silicon carbide 'molecular'; they are giant covalent network solids.
• Missing that argon (a noble gas) forms a molecular solid held by weak dispersion forces. …