Strong (100-1000 kJ mol^-1)
1. Macromolecular covalent bonds which exist between atoms in a crystal lattice (e.g., diamond, graphite, silica [SiO₂], borazon []). Characteristics of macromolecular solids are a high melting point and electrical nonconductivity
2. Ionic bonds (e.g., NaCl, KCN). Characteristics of ionic solids are a high melting point and high electrical conductivity in the liquid phase.
Intermediate (10-50 kJ mol^-1): Hydrogen bonds which form between a hydrogen atom and a more electronegative atom in the same or another polar molecule (e.g.,H₂F₂,, H₃O⁺).
Weak (0-10 kJ mol^-1):
1. Van der Waals forces (a.k.a., London dispersion forces) which result from instantaneous fluctuations in electron density distribution in nonpolar compounds (e.g., solid noble gases, CX₄, CO₂, C₆H₆).Characteristics include low melting point, softness, a tendency to sublime, poor heat conductivity, and nonconductivity of electricity.
2. Dipole attractions resulting from permanent dipole structures within a molecules (e.g., H₂O, NH₃). Characteristics of polar compounds are low to moderate melting point, variable hardness, and brittleness.
3. Metallic network forces characterized by a cationic network with an electron cloud distributed in the interstitial areas (e.g., Cu, Zn, Cr). Characteristics include luster, malleability, high heat and electrical conductivity