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Solid Sphere Model
John Dalton observed that elements combine to form compounds in whole-number ratios and that matter is not created or destroyed during chemical reactions. Dalton concluded that elements are made up of small, spherical, indivisible pieces called atoms.
John Dalton theory is composed of five parts: 1.Atoms are the building blocks of matter. 2. Atoms are indivisible. 3. Atoms of the same element are identical. 4. Atoms of different elements are different. 5.Whole number ratios form compounds. -
Plum Pudding Model
J.J. Thomson theorized that atoms contain electrons, or negatively charged particles. (Cathode RAy experiment.) He believed that atoms were composed of a positively charged fluid and negatively charged electrons. -
Nuclear Model
Ernest Rutherford developed the idea that atoms contained a small, massive, positively charged area, or nucleus. (Rutherford conducted the Gold Foil Experiment.)Rutherford reasoned that an atom could be divided into a dense, positively charged nucleus and circling, tiny, negatively charged electrons. -
Solar System Model
Neils Bohr developed an atomic model in 1913 that had electrons circling in orbit around a positive,massive nucleus. The different electrons orbited at different distances from the nucleus. Bohr believed that light would appear from the atom when the atom was exposed to a flame because electrons were falling to a different level in the atom. -
Proton Model
Ernest Rutherford added to his previous atomic model in 1918. Rutherford further stated that the nucleus of an atoms contains protons, or small, positively charged particles. -
Electron Cloud Model
Werner Heisenberg developed the modern atomic model in 1927. Heisenberg proposed a cloud model of an atomic because he reasoned that the location of electrons within an atomic could not be exactly pinpointed. The "cloud" of the model suggests possible locations of electrons. -
Electron Cloud Model (Continued)
James Chadwick further developed the modern atomic model in 1932. Chadwick observed neutrons, uncharged particles, within the nucleus of an atom. He believed neutrons were significant in order to hold the protons of the nucleus together.
