Review the atomic ideas of the early Greek thinker, Democritus, and his idea of cutting matter into the smallest possible piece, almost invisible. This was called an atom (or A-tom). The next major theory was that of John Dalton, who pictured the atom as a solid, smooth ball in which each atom of the same element had the same properties, like mass, and could combine in distinct ratios. Atoms of different elements had different properties. There was no explanation as to how these atoms combined, but he theorized that they could not be changed into other elements. The attempt of the Alchemists to change base metals into gold with no success was used to verify Dalton's theory. Thompson was next to show that the neutral atom possessed a negative particle he called the electron. He theorized that there must also be a positive section of the atom which neutralized the negative electron. His theory involved electrons implanted in a positive area like raisins in rice pudding.