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Understanding of Matter timeline

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Fergus B

on 20 February 2014

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Transcript of Understanding of Matter timeline

Understanding of Matter
By Fergus Selkirk-Bell
Ancient Greeks (500-400 BC)
500-400 BC-Democritus
Democritus stated that each type of matter was made up of indivisible elements; these being atoms. He proposed the idea that atoms were eternal and could not be destroyed. He made this theory with philosopher and his teacher Leucippus.
500-400 BC- Aristotle
Aristotle stated that everything was made out of four elements- earth, wind, fire and water. He rejected Democritus' theory that atoms were eternal and indivisible.
17th and 18th centuries
1660-Robert Boyle
Known as the 'Father of Chemistry', Boyle was Ireland's most influential scientist who primarily studied gases. He proposed that elements are composed of 'corpuscles' or different types and sizes and have the ability to organise themselves into groups that represent different chemical substances.
He suggested that if the volume of a gas decreased, the pressure increases proportionally. This became known as
Boyle's Law
Boyle was also able to distinguish between a mixture and a compound and gave 'element' the meaning that we use for it today.
1778-Antoine Lavoisier
Antoine Lavoisier was a French scientist who was known for his experimentation skills. He became known as the 'Father of modern chemistry'.
Lavoisier proved that the mass of the substances in a reaction is equal to the mass of the reactants. This is referred to as the
Law of Conservation of Mass
He was able to disprove Aristotle's theory that everything is made out of four elements (earth, wind, fire and water). He did this by showing that water is a compound, that air is a mixture, that earth contains different elements and that fire is a chemical process that uses oxygen.
He also clarified the distinction between elements and compounds.
1803-John Dalton
John Dalton was an English chemist and physicist. He developed the

modern atomic theory
Dalton studied weather and through observations of weather patterns and fog, he realised that water could exist as a gas that mixed with, and occupied the same space as, air. He realised that solids cannot occupy the same space, e.g. ice and air.
He found that all matter must be made up of tiny particles. He also found that in gas, the particles floated around freely. He then extended his theory to all matter.

19th century
Dalton's theory-
1. All matter is composed of indivisible particles called atoms.
2. All atoms of a given element are identical; atoms of different elements have different properties.
3. Chemical reactions involve the combination of atoms, not the destruction of atoms.
4. When elements react to form compounds, they react in simple whole number ratios.
1897-Joseph John Thomson
J.J. Thomson was a British physicist who discovered the
. He did this by a number of experiments in a high-vacuum cathode-ray tube. During his experiments he found that the electrons that made up the cathode-rays, could be deflected by magnets or electrically charged plates. This made him conclude that electrons must be part of the atoms of all elements.
Thomson made an atomic model in 1904. He proposed that atoms were positively charged spheres with small negative
electrons loosely embedded in them like plums
in a plum pudding. This model became known
has the
'plum-pudding' model
. He also stated
that every element has a different number of
20th century
1911-Ernest Rutherford
Ernest Rutherford was a physicist from New Zealand who was a student of J.J. Thomson's. He used radioactivity to investigate that structure of the atom. He and his students Hans Geiger and Ernest Marsden, did an experiment to test the 'plum-pudding' atomic model. They hit a thin gold foil with positively charged alpha particles from a radioactive source. Rutherford was expecting all of the particles to pass through the foil but instead a small amount bounced back. This meant that there was something in the centre of the atoms- the nucleus.
This experiment disproved Thomson's model and he
proposed a new atomic model:
the nuclear model
of the atomic structure
He also suggested the existence of neutrons
within the nucleus.
1932-James Chadwick
James Chadwick was a British scientist. He performed an experiment that involved hitting a sample of beryllium with alpha particles. He found that the beryllium that was being hit, was giving off a ray; he had discovered the
. As the alpha particles hit the beryllium, they displaced unchanged particles called neutrons.
Chadwick's experiment
proved Rutherford's hypothesis

that neutrons exist within the nucleus
Atomic models used today
1913-Neils Bohr
Neils Bohr was a Danish physicist whose proposed model of the atom is still used today,
the Bohr Model
. Bohr suggested that electrons orbited the nucleus in shells and the number of electrons in the outer orbit determines the properties of the element. Electrons cannot exist between the orbits. Although an electron cannot lose energy while orbiting a nucleus, it can receive more energy (by a flame or electric current). If this occurs, the electron would move to a higher orbit; moving from the ground
state (lower energy level) to an excited state.
1926-Erwin Schrodinger
Erwin Schrodinger was an Austrian physicist who used the quantum theory to extend Bohr's model. He used a mathematical equation to describe the location and energy of a hydrogen atom. From this he developed
the quantum-mechanical model
. The electron is not moving on a specific path but is found in an orbit around the nucleus. In this case, it is visualised as a cloud of negative charge. The cloud gets denser where the chances of finding the electron is higher.
Taylor, N., Derbogosian, M., Ng, W., Stubbs, A., Stokes, R., Brown, S., Raphael, S. & Moloney, J., (2007)
Study On Chemistry 1
, John Wiley & Sons Australia, Ltd, Milton, Queensland

ABCTE, (2007) Modern Atomic Theory: Models [online],
http://www.abcte.org/files/previews/chemistry/s1_p6.html, Viewed 16 February 2014

BBC History, (2014) Robert Boyle (1627-1691) [online],
http://www.bbc.co.uk/history/historic_figures/boyle_robert.shtml, Viewed 16 February 2014

Chemical Heritage Foundation, (2010) Antoine-Laurent Lavoisier [online],
http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/early-chemistry-and-gases/lavoisier.aspx, Viewed 16 February 2014

Chemical Heritage Foundation, (2010) Ernest Rutherford [online],
http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/rutherford.aspx, Viewed 16 February 2014

Chemical Heritage Foundation, (2010) Joseph John Thomson [online],
http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx, Viewed 16 February 2014

Chemical Heritage Foundation, (2010) Robert Boyle [online],
http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/early-chemistry-and-gases/boyle.aspx, Viewed 16 February 2014

Nobelprize.org, (2014) Erwin Schrödinger - Biographical [online],
http://www.nobelprize.org/nobel_prizes/physics/laureates/1933/schrodinger-bio.html, Viewed 16 February 2014

Universe Today, (2010) Democritus Atom [online],
http://www.universetoday.com/60058/democritus-atom/, Viewed 16 February 2014

Visionlearning, (2003) Atomic Theory 1: The Early Days [online],
http://www.visionlearning.com/en/library/Chemistry/1/Atomic-Theory-I/50, Viewed 16 February 2014

Visionlearning, (2003) Early Ideas about Matter: From Democritus to Dalton [online],
http://www.visionlearning.com/en/library/Chemistry/1/Early-Ideas-about-Matter/49, Viewed 16 February 2014

Robert Boyle
Antoine Lavoisier
John Dalton
Joseph John Thomson
Ernest Rutherford
James Chadwick
Neils Bohr
Erwin Schrodinger
Full transcript