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John Dalton
John Dalton Atomic ModelIn 1803 English chemist John Dalton discovered the atom. He discovered that certain gases only could be combined in certain proportions even if two different compounds shared the same common element or group of elements. His findings led him to hypothesize that elements combine at the atomic level in fixed ratios. Dalton Developed the Atomic Model. -
JJ Thomson
JJ Thomson Atomic ModelJJ Thomson discovered and identified the electron by showing that cathode rays were composed of a previously unknown negatively charged particle. Thomson imagined that the electrons were orbiting in a sea of positive charge, which was later disproved by Ernest Rutherford. -
Electron Cloud Model
Electron Cloud ModelThe electron cloud model is an atom model wherein electrons are no longer depicted as particles moving around the nucleus in a fixed orbit. The electron cloud model describes their probable location around the nucleus. The model of course doesn’t show us the exact location of the electrons around the nucleus. -
Marie Curie
Marie Curie Atomic Modle
Marie Curie and her husband discovered the radioactive elements polonium and radium in the pure state. The Curie’s were not convinced that the radioactivity came from within the atom itself. -
Albert Einstein
Albert Einstein Atomic ModelEinstein devised a mathematical method of calculating the size of atoms and molecules. The paper Einstein wrote didn’t say much more about the waves of frequency and the relation to an atoms particles. -
Ernest Rutherford
Ernest Rutherford Atomic ModelErnest Rutherford discovered that an atom must have a positively charged center that contains most of its mass which is the nucleus that he called the proton which he discovered in his Gold Foil Experiment. Rutherford’s model was improved upon by Bohr. Electrons do not move around the nucleus like planets around the sun like Rutherford concluded. Rutherford also did not know that electrons were actually waves of energy. -
Niels Bohr
Niels Bohr Atomic ModelBohr explained what happens inside an atom and developed a picture of atomic structure. Bohr was also the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. The Bohr model however provides an incorrect value for the ground state orbital angular momentum. -
Louis de Broglie
Broglie Atomic ModelBroglie discovered that electrons can act like waves which helps explain some of the things electrons do that we had never been able to explain before. Broglie questions could you locate the precise position of the electron within the wave? German scientist Heisenberg proved this to be incorrect. -
James Chadwick
James Chadwick Atomic TheoryChadwick established that atomic number is determined by the number of protons in an atom. He also discovered the neutron. James Chadwick assumed things about the neutron that were not necessarily true, but these did lead to eventual discoveries in science that are true. -
Democritus
Democritus Atomic Model
Democritus’ theory is that everything is made up of atoms and atoms can’t be divided any further. Democritus theorized that atoms can’t be divided into smaller particles. This was later in history disproven that atoms can be split into smaller parts, the proton, neutron and electron.
