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These information was actually introduced by Democritus c.350BC
- developed a theory which outlined that the universe was made of empty space, and an almost infinite number of indivisible, tiny particles, called atoms.
- Showing these atoms were different in form, position and arrangement.
- Describe how natural phenomena's occurred because of the interaction and/or movement of atoms.
- Formed the beginning of the atom and his theory set up the research and discoveries that would follow. -
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Isaac Newton introduced the laws on gravitation (every object in the universe attracts every other object with a force, gravitational force)
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- stating each element was a unique substance and all the atoms forming a particular element were similar and identical in weight. Dalton in 1803
- stating that all matter is made of minute particles called atoms-atoms cannot be broken down into smaller particles-atoms of the same element are alike-atoms join together in different atoms
- suggested a simple rule: if two elements form one compound, assume the compound has only one atom
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G.J. Stoney in 1894
- introduced the electron as the fundamental unit of electricity.
- stated that the electron was a twentieth (1o-20) of a quantity of electricity otherwise known as an ampere.
- introduced the term 'electron' in 1891 but introduced the concept as early as 1874. -
J.J. Thompson in 1897
- proposed that atoms were divisible and consisted of electrons.
- show that atoms had no charge thus the conclusion that atoms were made of negatively charged particles would be incorrect.
- proposed that the electrons were distributed throughout a sea of positively charged particles like plums were distributed throughout a plum pudding -
Planck in 1900
- explained the glowing of hot matter with quanta
- explained small discrete units of energy being radiated from the matter. -
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Nagaoka in 1903
- developed an analogy for the layout of an atom.
- proposed the Saturnian Model which showed that the movement of electrons around the positively charged nucleus was due to a huge nucleus - Saturn's rings are stable because they are orbiting such a massive planet.
- Proved that electrons moving around the nucleus were bound by electrostatic forces- like gravitational pull keeping the rings of Saturn revolving. -
Millikan in 1909
- conducted an oil drop experiment many times and found the charge of the electron to be 1.592 × 10−19 coulomb. His answer is lower than the modern value probably because he measured air viscosity wrong,
- he found that :a. Charge is quantisedb. The Electron is a sub atomic particle -
E. Rutherford in 1911
- made a model of the subatomic particles in 1911. In this model there was a central charge surrounding by orbiting particles.
- His model portrayed the nucleus as very small, but he said it made up most of the weight of the atom. This analogous to the solar system. -
H.G.J Moseley in 1914 introduced law that outlines that the ''square root of the frequencies of lines in atomic x-ray spectra depends linearly on the atomic number of the emitting atom.''
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Bohr in 1922
- introduced 'shells' in atoms.
- produced this as a reason why electrons are stable in an atom. -
James Chadswick in 1932 proved the existence of the neutron- it's mass was 0.1% more than the proton's and it had a neutral charge.