Atomic Theories and Models

• Atoms are building blocks of matter that makeup everything in the universe.
• Democritus was the first to propose the idea of atoms whereas Aristotle believed that everything was made up of four elements: earth, wind, water, and fire.
• the word atom originates the the word "atomos"
• John Dalton proposed the first atomic theory where atoms are microscopic balls.
• J.J. Thompson discovered the electrons and proposed the plum pudding model.
• Ernest Rutherford the nucleus and protons, and proposed the Rutherford Model of the atom.
• James Chadwick, while working with Rutherford, discovered neutrons.
• Niels Bohr improved the Rutherford Model by proposing that electrons move in orbits around the nucleus. This model is called Bohr's Model or the planetary model.
• A quanta is a single packet of matter or energy. It refers to the minimum amount of energy needed for change.
• quantum leap refers to electrons moving from one orbit to another.
• The Bohr-Sommerfeld Model was introduced by N. Bohr and Arnold Sommerfeld. It proposed elliptical orbits, allowance for electron orbiting motion, and relativistic mass effect.
• Erwin Schrodinger used wave-particle duality of the electron to develop and solve a complex mathematical equation that accurately

  described the behavior of the electron in a hydrogen atom.
• Erwin Schrodinger created the quantum model of an atom, proposing electron clouds instead of orbits, stating that an electron's position cannot be directly defined.
• Electron clouds are regions where there is a high probability of finding an electron.
• James Maxwell showed that a charged particle moving through an electromagnetic field would continuously radiate energy.
• Werner Heisenberg proposed the uncertainty principle, which states that it is impossible to determine both the momentum and position of an electron.
• Louise de Broglie and Erwin Schrodinger proposed that light and atoms might have the same properties.