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Democritus
Democritus believed that atoms cannot be divided or that they are indivisible. Also, he believed that all matter is made up of particles called atoms. Democritus was incorrect that these tiny particles are indivisble, atoms can be divided. -
John Dalton
Dalton proposed that that all matter is made up of spherical individual particles, that can’t be divided, called Atoms. He developed the theory to explain why elements in a compound always join in the same way. He found this out through his studies of gases. A problem with Dalton’s Theory is that he stated that atoms are indivisible, which they are not. -
JJ Thomson
Thomson discovered the electron using a cathode-rat tube in his experiments. He placed two electric plates (one positive one negative) on the path of the beam and the beam bent towards the positively charged plate. Through his observation of the experiment he discovered the electron. -
Electron Cloud Model
The electron cloud model represents the probable locations of electrons in an atom. Scientists like Ernest Rutherford, Niels Bohr, and Werner Heisenberg contributed to the discovery of the model. Electrons travel around the nucleus in a cloud, thus the name electron cloud model. -
Albert Einstein
Einstein made a great contribution to the atom theory. He used his theories in quatum physics to help him explain his theory. His theories were evidence that atoms exist and showed how they are structured. -
Ernest Rutherford
Rutherford performed an experiment with gold foil to find out the structure of an atom. He found out that an atom has a positively charegd nucleus in the middle of electrons orbiting around it. Rutherford discovered that the center of an atom is dense and has a positive charge. -
Niels Bohr
Neils Bohr discovered that electrons travel around the nucleus in a cloud called the electron cloud model. Bohr used the information Ernest Rutherford came up with to discover his theory. -
James Chadwick
James Chadwick discovered the neutron in the atom. He also established that the atomic number is determined by the number of protons in an atom.
