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Jan 1, 1000
Democritus (470-360 BC)
Democritus was a Greek philosopher. He put forward the idea that matter could be divided into smaller particles until it became small, hard, indivisible particles, which he called atoms. Taken from Excel Science Handbook - Years 9 - 10 -
Isaac Newton (1643 - 1727)
English physicist, Isaac Newton, proposed a mechanical universe with small solid masses in motion. Taken from Atomic Structure Timeline - http://atomictimeline.net/index.php -
John Dalton (1766 - 1844)
Dalton was an English scientist. He proposed in 1803 that matter was made of indivisible particles or atoms and that each element is made up of its own characteristic atoms. Compounds contain atoms of different elements joined in a simple ratio. Taken from Excel Science Handbook - Years 9 - 10 Taken from Excel Science Handbook - Years 9 - 10 -
George Johnstone Stoney (1826 - 1911)
In 1894, Anglo-Irish born Stoney proposed that electricity was made of negative particles he called electrons. Taken from Atomic Structure Timeline - http://atomictimeline.net/index.php -
Sir John Thomson (1856 - 1940)
Thomson was a British physicist. In 1897, he discovered the electron and showed that electrons are negatively charged particles and smaller and lighter than the smallest atom, hydrogen. Taken from Excel Science Handbook - Years 9 - 10 -
Max Planck (1858 - 1947)
Planck, a German physicist, used the idea of quanta (which are discrete units of energy) to explain hot glowing matter. Taken from Atomic Structure Timeline - http://atomictimeline.net/index.php -
Hantaro Nagaoka (1865 - 1950)
In 1904, Nagaoka developed an early, incorrect "planetary model" of the atom. The model was based around an explanation of the stability of the Saturn rings (the rings are stable because the planet they orbit is very, very massive). The model made two predictions: Saturn has a very big nucleus and the electrons revolving around the nucleus are bound by electrostatic forces. Taken from Wikipedia - Hantaro Nagaoka -
Robert Andrews Millikan (1868 - 1953)
In 1909, American physicist, Millikan worked on an oil-drop experiment in which he measured the charge on a single electron. -
Sir Ernest Rutherford (1871 - 1937)
Rutherford was a New Zealand born British physicist. In 1911, he proposed that an atom had a small positive nucleus that was surrounded by an equal number of orbiting electrons. Therefore creating the 'empty space' model. Taken from Excel Science Handbook - Years 9 - 10 -
Henry Mosely (1887 - 1915)
Henry Mosely, an English physicist, used x-ray tubes, determined the charges on the nuclei of most atoms. He wrote "The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganise the periodic table based upon atomic number instead of atomic mass. Taken from Atomic Structure Timeline - http://atomictimeline.net/index.php -
Niels Bohr (1885 - 1962)
In 1922, Bohr was awarded a Nobel Prize in Physics for his fundamental contributions to the understanding of the atomic structure and quantum mechanics. In 1913, he proposed an atomic model where electrons travel around the nucleus in fixed orbit and each orbit has a definite amount of energy. Taken from Wikipedia - Niels Bohr
Taken from Excel Science Handbook - Years 9 - 10 -
Sir James Chadwick (1891 - 1974)
Chadwick is a British physicist who discovered the neutron in 1932. He found it to be a similar mass to the proton. Taken from Excel Science Handbook - Years 9 - 10
