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Period: 200 to
History of the Atomic Model
How much development it took to finally get the correct model of the atom. -
400
Democritus, Greece
Democritus, a greek philospher suggested that matter is made of tiny particles called atoms. The word came from the greek word "atomos." which stands for indivisible. -
450
Aristotle, Greece
Greek philospher, Aristotle still belived in the four element theory ignoring the recent atomic model. Aristotle persuaded everyone enough for them to belive the four element model for almost 2000 years. -
John Dalton, Manchester, England
John Dalton, an english chemist, meteorologist, and physicist had come up with a theory saying that all matter is made of particles called atoms. Each contains its own type of atoms with its own mass. When atoms from different elements link together, they form molecules which then create a compound. Finally, atoms cannot be created, destroyed or subdivided. John Dalton said that atoms are like billiard balls because they are like featurless balls. However, this was soon to be proven wrong. -
Dimitri Mendeleev, Russia
Dimitri Mendeleev was a russian chemist who had created the most important table in science, the periodic table. The periodic table is a list of all elements known to mankind. It is used to describe the types of atoms in each element like the amount of mass in sodium atoms. -
Antoine Henri Becquerel, Paris, France
Henri Becquerel, a french phycisist had discoverd radioactivity. He had placed a mineral in his study that contained high amounts of uranium and near it were some special sheets of paper. When he returned to his study, the paper had made an exact model of the mineral. Along with further studying, Henri Bequerel had discovered radioactivity which led to the discovery of another atomiv theory. -
Joseph John Thomson, Manchester, England
J. J Thomson, an english phycisicist had revised the atomic model and was not satisfied. As he began to do experiments, he discovered small negative charges called electrons. This model was called the raisan bun model because like a raisan bun, atoms are embedded with electrons. The rest of the atom is made of positive space called protons. -
Hantaro Nagaoka, Japan
Hantaro Nagaoka, a japanese phycicist had begun to consider the atomic model. As he began experimenting, he came up with a new analogy. Instead of having electrons embedded in the atom like J. J Thomsons Raisan Bun analogy, Hantaro Nagaoka explained that the electrons circled the atom like the planet saturns rings. -
Ernest Rutherford
Ernest Rutherford, an english phycicist and chemist wanted to put J. J Thomsons and Nantaro Nagaokas theories to the test. Using Henri Bequerels latest discovery of radioactivity, Rutherford created an experiment to test the two theories. He had placed a small amount of radioactive waste in a lead box which pointed towards a thin sheet of pure gold. Based on Thomsons theory, Rutherfords hypothesis was that the radioactive energy would pass through the gold sheet with ease. But, some energy came -
Marie Curie,France
Marie Curie was a french phycicst who conducted experiments on radioactivity after it was discoverd by Henri Becquerel in 1896. In 1911, bothe Marie Curie and Henri Becquerel had won the Nobel Prize. -
Neil Bohr, Denmark
As Rutherfords experiment played out, Neil Bohr was helping Rutherford with the experiment. To everyones surprise, most of the energy went straight through the gold sheet but some of it bounced back. Finally, through lots of development, Neil Bohr resolved that in the center of every atom, their is a dense amount of positive energy called the nucleas. Also, orbiting the nucleas are small electrons that causes the atom to have electrical charges. Its almost like our solar system. -
James Chadwick, England
James Chadwick was an english phycicist who discovered yet another particle inside the atom, the neutron. Neutrons are small particles located within the nucleas of the atom. Neutrons are empty spaced meaning they do not have a mass.
