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400 BCE
The Early Greeks and Their Theories
400 BC: This is around the time when the Early Greeks proposed that all "matter" could be made up of only four "substances": Fire, Earth, Wind, and Water. -
400 BCE
Democritus and His NEW Theory
However, the Greeks and their stuck up theories were about to be challenged. Democritus, years later, towards the end of the 5th century, proposed that all matter, was in fact, individual indestructible particles which he called "atoms". However, he had no scientific evidence to prove his theory. The picture provided illustrates the idea how the early atomic theory stated that different materials were made up of differently shaped atoms. -
Robert Boyle and His Elemental Discoveries
In the 17th century, Robert Boyle discovered that Gold and Silver, are in fact, "elements". His ideas and theories began getting slowly accepted (the fact that there exists more than just fire, water, earth, and wind). Hence, with this discoveries, the Early Greeks and their theories had been debunked. -
Dalton: Atomic Properties + Debunking Democritus
Around the 19th century, Thomas Dalton came forward and suggested his atomic theory. He discovered several atomic properties as we know them today. He thought atoms were like marbles. This revolutionary man of science said:
1. All elements are made of atoms and cannot be divided.
2. Only atoms of the same elements are identical.
3. Atoms can physically mix together or combine in whole number ratios
4. Atoms can never change their identity, however, they can be rearranged (like legos). -
Thompson And His Plum Pudding
J J Thompson seemed to have made breakthrough discoveries by suggesting a very interesting, never though of, model of the atom. Suggesting that the atom was not just any spherical tiny object, but more like a plum pudding (before the discovery of the atomic nucleus). Fun fact: He called electrons, "corpuscles". -
Rutherford and His Clapback.
Ernest Rutherford, the man-the myth-the legend, has set the foundation for the modern day atomic model. By performing his famous, "Geiger-Marsen" experiment and his 1911 analysis, he snapped back at Thompson and proved that the "plum pudding" model was 100% wrong. -
Bohr and the Orbits
Bohr theorized that the electrons in the atom must move on prescribed orbits, and energy transfer occurs in defined quantities. He proposed that the atom was like our solar system, except that the attraction was provided by electrostatic forces, and not gravity. -
Louis De Broglie and Waves
Louis de Broglie, a Nobel Prize Winner predicted the wavy nature of electrons. He said that electrons move in waves, and not circular orbits (see reference image). He also said that all and every matter has wave properties. -
Heisenberg Uncertainty Principle
In 1925, 23 year old Werner Heisenberg discovered the uncertainty Principle. For the atomic model, the theory indirectly stated that it is not possible to know both the energy and the location of an electron. Technical Terms: "values of certain pairs of variables cannot both be known with complete precision not...due to the limitations of the researcher’s ability...but...due to...nature of the system..."
Helpful Video: Evolution of Atomic Model + Heisenberg Principle -
Schrodinger, Electrons, and ~Waves~
Austrian physicist, Erwin Schrödinger improved upon the Bohr Model by describing the likelihood of finding an electron in a certain position (using mathematical calculations). His model is known as the quantum mechanical model. As illustrated here , he theorized that electrons are particles AND waves, and do not remain fixed in a 2D orbit. -
Chadwick and the Neutrons
On a beautiful day in 1932, James Chadwick just 'bombarded' beryllium atoms with alpha particles. The result of this was a spooky radiation, and Chadwick interpreted this radiation as being composed of particles with a 'neutral electrical charge' and with the same approximate mass of a proton. Now, these particles are called neutrons!
