Atoms may or may not exist independently, but most of them undertake chemical reactions to form ions and molecules which further combine in large numbers to form matter that we see, feel and touch. A compound is a distinct group of atoms held together by chemical bonds. Just as the structure of the atom is held together by the electrostatic attraction forces, the stability within chemical bonds is also due to electrostatic attractions. There are two major types of chemical bonds: covalent bonds and ionic bonds.

Key Terms

• Particle: all atomic units such as molecules, atoms, protons, neutrons, electrons, etc. are simply referred to as particles.