5. The quantum world of the atom

‘The quantum world of the atom’ considers the profound discoveries of the early twentieth century that exposed the inner structure of the atom and the revolutionary new physics of quantum mechanics—the behaviour of matter on very small scales. At the microscopic level, ‘particles’ of matter resemble waves, a feature that enables us to understand the structure, stability, and properties of atoms. Key discoveries and concepts are described: the fundamental constant of nature, Planck’s constant; Heisenberg’s uncertainty principle; the Schrödinger equation; quantum tunnelling; the wavelike characteristics of microscopic particles; and the two types of particles, fermions and bosons.