Quantum Theory of the Atom

by Contributing Writer

Overview

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Quantum theory explains the discrete nature of energy levels in microscopic systems comprised of atoms, the smallest part of an element that retains the chemical properties of that element.
Atom Discovery

Greek philosopher Democritus hypothesized in 450 B.C. that matter was made up of atomos, substances infinitely smaller than indivisible particles, but it was not until the 1800s that the atomic theory took hold. British physicist J.J. Thomson discovered electrons in 1897.

Atomic Framework

Atoms are a complex structure. They consist of a nucleus composed of protons and neutrons. Electrons orbit the nucleus like our planetary system.
Particles of the Atom

The proton has the positive charge and determines the atomic number on the configuration table. The neutron has no electrical charge and determines the isotope that slightly separates the protons. The electron has a negative charge and determines the ion. When the nucleus kinetics becomes unstable, atoms turn radioactive.
Planetary Model

Danish physicist Niels Henrik David Bohr's atom model postulates that the electron in an atom's orbit does not emit energy. Emission only occurs when the electron jumps from one stationary orbit to another.
Cloud Model

Erwin Schrodinger, Austrian theoretical physicist, hypothesized that an electron is found in a random cloud-like area. The electron wave can be found in a given region of space at a given time.
Particles and Waves

Quantum mechanics explains all the known properties of individual atoms. There is no boundary between particles and waves.