Elements & Atoms Atomic theory grew as a series of models that developed from experimental evidence. As more evidence was collected, the theory and models were revised.

Elements & Atoms Dalton Model – atoms are like smooth, hard balls that could not be broken into smaller pieces. (See p. 8 – Summary of Dalton’s Ideas) Solid Sphere Model or Billiard Ball Model proposed by John Dalton

Elements & Atoms Thomson Model – atoms have negatively charged electrons embedded in a positive charge. Plum Pudding Model or Raisin Bun Model proposed by J.J. Thomson

Elements & Atoms Rutherford’s Gold Foil Experiment – most particles pass through foil in straight line, but a few were strongly deflected. This led to proposal of Rutherford Model, small, positively charged nucleus in center of the atom. Rutherford Model of a lithium atom.

Elements & Atoms Bohr’s Model – electrons move in specific orbits around the nucleus of an atom. The Bohr atom

Elements & Atoms Cloud Model – electrons move rapidly in every direction around the nucleus.

Elements & Atoms Modern Atomic Model – nucleus, which contains both protons and neutrons, is surrounded by a cloudlike region of electrons.