Intermolecular and interatomic bonds

The two main types of intermolecular bond are ionic and covalent, although weaker bonds, essential for intermolecular interactions, also exist. The structure of the component atoms determines the type of bonds within the molecule.

Atomic structure

When considering atomic structure, certain definitions aid understanding:

• Atom – the smallest part of an element that can take part in chemical reactions

• Element – a group of atoms all having the same atomic number

• Molecule – a combination of atoms which is the smallest unit of a chemical substance that can exist while still retaining the properties of the original substance

• Atomic number – the number of protons in each atom of an element

Knowledge of the basic structure of atoms is important in understanding the types of intermolecular bond and their functions. A schematic view of atomic structure is shown in Figure PC1.

An atom consists of a nucleus (central core) of neutrons and protons, surrounded by a cloud of negatively charged electrons. Figure PC2 shows the properties of these components. The charge of an atom is the number of protons minus the number of electrons. It is clear that almost all the mass of an atom is in the nucleus. The number of protons (atomic number) defines the element, and the atomic mass is close to the combined masses of protons and neutrons in the atom. Elements may exist with different numbers of neutrons in the nucleus while having the same atomic number.