Bonding forces are forces of attraction or repulsion which act between neighboring particles such as atoms, molecules or ions. Bonding force determines the elastic modulus (or Young's modulus) of a material (how stiff a material is). The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds, and "weak bonds" such as dipole-dipole interactions and hydrogen bonding. Since interaction energy and bonding force are directly related, the stronger the bond energy, the harder is to move the atoms, such as to melt the solid or to evaporate its atoms.
Intermolecular forces (IMFs) are forces of attraction or repulsion which act between neighboring particles (atoms, molecules, or ions). They are weak compared to the intramolecular forces, the forces which keep a molecule together. For example the covalent bond, involving the sharing of electron pairs between atoms is much stronger than the forces present between the neighboring molecules. They are an essential part of force fields frequently used in molecular mechanics.