Atoms

By ARIZ1
  • 450 BCE

    Democritus

    Democritus
    Democritus of Abdera, named the building blocks of matter atomos, meaning literally “indivisible,” about 430 bce. Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped

  • John Dalton

    theory of chemical combination, first stated by John Dalton in 1803. It involves the following postulates: Elements consist of indivisible small particles (atoms). All atoms of the same element are identical; different elements have different types of atom. Atoms can neither be created nor destroyed.

  • Michael Faraday

    Michael Faraday discovered that atoms have an electrical component. He discovered this when studying the properties and reactions of electrolysis, which runs an electrical current through water or other liquids.

  • J. J. Thomson

    Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson's plum pudding model of the atom had negatively-charged electrons embedded within a positively-charged "soup

  • Robert Millikan

    Millikan's work demonstrated that electrons did have a discrete, quantifiable charge. Thomson had also already calculated the charge-to-mass ratio of an electron, so once Millikan was able to measure the elementary charge, the mass of an electron could also be calculated.

  • Ernest Rutherford

    In 1911, Rutherford described the atom as having a tiny, dense, and positively charged core called the nucleus. Rutherford established that the mass of the atom is concentrated in its nucleus. The light, negatively charged, electrons circulated around this nucleus, much like planets revolving around the Sun.