-
400
Democritus
Democritus believed that the smallest piece of matter was the atom, and that it was indivisible and everything was made up of them. However, his idea was at first ignored by everyone and it wasn't until the 1800's that people finally started to think about it.
Democritus's atomic model was just a circle with nothing in it. This was the first concept of the atom, so there were no previous models for this to contradict.
Democritus's theory was cast aside in favor of Aristotle's, they often argued. -
Antoine Lavoisier
Lavoisier used an experiment to establish the Law of Conservation of Mass. He also discovered that Oxygen combined with Hydrogen appeared to be water. He disproved the phlogiston theory, and discovered that animals create energy through combustion. He invented chemical names we still use today such as sulfuric acid, sulfates, and sulfites. And he believed that an atoms existance was impossible. -
Henri Becquerel
While experimenting with light on Uranium salts Becquerel discovered that Uranium salts would spontaneously emit a radiation. After researching it he realized he had discovered radioactivity.
He shared a nobel prize with the Curie's in 1903. -
Marie and Pierre Curie
After Becquerel discovered radioactivity the Curie's were inspired and began researching. They isolated the elements Radium and Polonium, and developed methods for the separation of radium from radioactive substances, so that they could study it's characteristics. -
Max Planck
Planck discovered the relationship between energy and the frequency of radiation. He also first started Quantom Theory; revolutionizing the human understanding of atomic and subatomic processes. -
J. J. Thompson
Thompson discovered small negatively charged particles inside of the atom, electrons. So he theorized that the atom was a bunch of small negatively charged particles floating around in a positively charged space.
He added upon Dalton's theory by putting electrons on the inside of it. His model, the Plum Pudding model, looked like many negatively charged particles, plums, inside of a positively charged space, pudding.
Thompson was Rutherford's teacher, who would later disprove his theory. -
Ernest Rutherford
Rutherford conducted an experiment and discovered that the atom actually had a positively charged core, the nucleus, which was orbitted by electrons.
Rutherford disproved Thompson's model by showing that electrons orbitted a nucleus and did not float inside of positively charged space. His model looked like a nucleus with orbits around it containing electrons.
Rutherford was Thompson's student, Chadwick's teacher, and Bohr's teacher. -
Niels Bohr
Bohr theorized that the electrons orbitted around the nucleus in a circular pattern. He only applied quantum theory to Rutherford's model and made it easier to predict energy levels.
According to Bohr the atom looked like a nucleus with electrons orbitting it in a circular pattern.
Bohr was a student of both Thompson and Rutherford. He also worked alongside Werner Heisenberg. -
Henry Moseley
Moseley discovered that the wavelengths of the X-ray spectral lines of the elements, which showed that the ordering of the wavelengths of the X-ray emissions matched with the ordering of the elements by atomic number. Because of this the modern Periodic Table is organized by atomic number. -
John Dalton
John Dalton used the concept of Democritus's theory to develop his own, which later became the foundation of chemistry. He believed that atoms were indestructable and the smallest form of matter there is, and that everything in the world was made up of them.
This theory was built upon Democritus's theory, and it looked the same as well. Represented as a circle with nothing inside of it. -
Robert Millikan
Millikan discovered the charge of an electron using the falling-drop method, and proved it was constant. This demonstrated the atomic structure of electricity. -
Werner Heisenberg
Heisenberg stated The Uncertainty Principle; saying the more we know about the position of a particle the less we know about its momentum and vice versa.
Heisenberg worked alongside Bohr. -
Erwin Schrödinger
Erwin Schrödinger developed an equation that accurately gave the energy levels of atoms. -
James Chadwick
Chadwick was the first to make the groundbreaking discovery of the neutron, a neutrally charged particle in the nucleus.
Chadwick was Ernest Rutherford's student. -
Aristotle
Aristotle believed that everything was made of four elements of matter; earth, fire, water, and air. This was a completely different view compared to the previous idea proposed by Democritus; which was that everything in the universe was composed of atoms.
Aristotle did not believe in atoms, so there was no atomic model for his ideas.
Aristotle had relations with Democritus, but it was mostly disagreements and arguments between them because their beliefs were so different.
