How Did Democritus And Leucipis Influence The Development Of An Atom

Democritus and Leucippus “invented” the idea of an atom back in fifth century B.C, with the Greek word ατoμoν (atom) meaning “indivisible” as at that time it was believed atoms could not be broken down into slightly smaller pieces. Over the years our ideas of atoms and atomic structure have changed, with Dalton, Thomson, Rutherford and Bohr all having differing opinions on how an atom is put together. “Billiard Ball Model”

For instance, John Dalton believed that atoms are the very small things of which everything (all matter) is comprised. Similarly to Democritus and Leucippus he believed dividing or destroying an atom was impossible, yet he was revolutionary in the idea that atoms of the same element were alike, while stating that atoms

Rutherford decided that if Thomson was correct with his model, than the atoms mass was widespread through the atom, thus if Rutherford was to shoot high velocity alpha particles (Helium Nuclei) towards an atom, there would be a small amount of substance to deflect the alpha particles. So Rutherford enclosed a radioactive source capable of emitting alpha particles in a protective lead shield. The emitted radiation was focused using a slit in the lead shield. A thin layer of gold sheet was placed in front of the slit, and a zinc coated screen (zinc to render it fluorescent) serving as a counter to detect alpha particles. When each alpha particle hit the fluorescent screen, a burst of light would be produced (called scintillation) only visible through a microscope attached to the back of the screen. The screen could be moved, so that Rutherford and his associates were able to decide upon whether the foil had deflected the alpha

Some particles were slightly deflected, implying interactions with other positively charged particles inside the atom. There were still other particles, left scattered at other angles, with a very small amount bounced back towards the source. Based on this, Rutherford concluded, only a positively charged and reasonably heavy target particle (such as the proposed nucleus) could provide such strong repulsion. He also went on to say the negative electrons proposed by Thomson as an electrical balance to the positive nuclear charge travelled in a sort of circular orbit, around the nucleus. The force of attraction between electrons and nucleus were then likened to the gravitational force between e revolving planets and the sun. Most of Rutherford’s planetary atom was open space and provided no resistance to the alpha