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Early Greek

History of Chemistry

By Hannah ParkPeriod 7

Time Line

445 BC

Empedocles of Acragas


435 BC

Leucippus of Miletus

384-323 BC

320 BC-300AD









Dalton's Model

Greek Model

Thomson's Model

Rutherford's Model

Bohr Model

Wave Model

~Empedocle of Acragas believed that there were 4 elements- earth, air, water, and fire.~Every object would be created with a specific ratio of these 4 elements. ~-- For example, the theory suggests that bones were composed in the ratio of 4:2:2 of fire:air:earth~ His belief was that "earth" means solids, "water" means liquids, "air" represents gases, and "fire" as an element.

~People were concerned about the origin of the universe.~Scientists began to explain natural phenomenon.~Philosophers of Miletus=most influential early thinkers~Thales of Miletus (582 BC) suggested that water was the basic substance of the universe.~Anaximander of Miletus challenged Thale's idea in 555 BC.~He suggested that world was created after the hot and cold separated.~Anaximenes of Miletus (535 BC) proposed that air was the main substance, and rarefaction or condensation changes one form to another.

~The wave model of the atom takes the basic idea of the Bohr model of the atom where there is a small dense nucleus surrounded by electrons, but the electrons are represented by a probability distribution instead of by discrete mathematical points. ~Thus they are often described as the "electron cloud".~Louis de Broglie and Erwin Schrodinger created the Wave Model.~It was named the "Wave Model" because electrons exhibit properties that are associated with waves.

~ Leucippus of Miletus built on the ideas of Empedocles. ~ He was able to develop the ideas into early atomic theory.~ He said that elements were composed of tiny invisible corpuscles called atoms.~ He believed that atoms varied in shape and size.~He also concluded that they combined in many different methods to produce different substances.

~Democritus, a Greek Philosopher, developed the greek atomic model.His atomic theory states that....1.All matter consists of invisible particles called atoms.2. Atoms are indestructible.3. Atoms are solid but invisible.4. Atoms are homogenous.5. Atoms differ in size, shape, mass, position, and arrangement.->Solids are made of small, pointy atoms.->Liquids are made of large, round atoms.->Oils are made of very fine, small atoms that can easily slip past each other.simply a round sphere with no electrons, protons, or neutrons.~Democritus created the first atomic model. ~His contribution helped people with understanding the idea of an atom, and helped other scientists to further look into atoms and its general makeup.

~Mostly known in Greece, China, India, Persia, and Egypt.~Alchemists= most intellectual people at the time~Alchemists were influenced by Aristotle's brilliant ideas.~Alchemists tried to find a way to transform cheap metals into gold.~The substance that provided this result is known as the Philosopher's Stone. ~Alchemists used salt, sulfur, and mercury as the main ingredients for the Philosopher's Stone.~~13th Century~~~alchemy and gold making were practiced throughout Europe.~Became very popular that Raymundus Lullus, famous alchemist, was ordered to make gold for King of England.~ 1317, Pope John XXII made an edict against gold making~Recipes spread, but the recipes did not work. the new "gold" turned out to have a density of only 12 g/mL.~Alchemists were fascinated in the search for the elixir of life that cures all and makes people live forever. ~1520, Philippus Aureolus Paracelsus produced cures to diseases with alchemy.

~However, there were some problems with Rutherford's model: for example, it could not explain the observation that atoms only emit light at certain wavelengths or frequencies. ~Niels Bohr solved this problem by proposing that the electrons could only orbit the nucleus in certain special orbits at different energy levels around the nucleus.

~John Dalton proposed that all matter is composed of very small ingredients that he called atoms. ~This was not a new concept for the ancient Greeks (especially Democritus) had proposed that all matter is composed of small, indivisible objects. ~When Dalton proposed his model, the electrons and the nucleus were unknown.~Dalton's theory tells us...1) All matter is made of atoms. Atoms are indivisible and indestructible.2) All atoms of a given element are identical in mass and properties3) Compounds are formed by a combination of two or more different kinds of atoms.4) A chemical reaction is a rearrangement of atoms.~Modern atomic theory still includes parts of Dalton's theory. Today, we know that atoms can be destroyed via nuclear reactions but not by chemical reactions. Also, there are different kinds of atoms (differing by their masses) within an element that are known as "isotopes", but isotopes of an element have the same chemical properties.

~After the electron was discovered by J.J. Thomson in 1897, people realised that atoms were made up of even smaller particles. ~However, the atomic nucleus had not been discovered yet.~In this model, the atom is made up of negative electrons that float in positive charge. ~With this model, Thomson abandoned his earlier "nebular atom" hypothesis in which the atom was composed of immaterial vorticies. ~Now, at least part of the atom was to be composed of Thomson's particulate negative corpuscles, although the rest of the positively-charged part of the atom remained somewhat nebulous and ill-defined.

~ Aristotle developed the idea of "properties of the elements", stating that different types of matter depend on a scientific balance of the qualitiesof the 4 components- hot, cold, wet, and dry.~ He knew there was someway to transform one element to another by changing this balance. ~ The idea was welcomed, partly at the excitement of changing metals into gold and other cheap materials into ojects of value. ~ The idea persisted for almost 2000 years.

~Rutherford carried out some experiments which led to a change in ideas around the atom. ~His new model described the atom as a tiny, dense, positively charged core called a nucleus surrounded by lighter, negatively charged electrons.~Another way of thinking about this model was that the atom was seen to be like a mini solar system where the electrons orbit the nucleus like planets orbiting around the sun. ~This model is sometimes known as the planetary model of the atom.

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QUESTIONS:1) My timeline helps prove that "science is tentative" because the timeline shows the progress of the scientific knowledge aquisition on atoms. Scientists build upon previous ideas and improve the theories, or they may disprove a previous theory and conclude another reasonable theory.2) The models of the atom evolved this way because scientists improve upon each other. At first, scientists have no knowledge on atoms and begin to imagine and wonder. They may come up with inaccurate beliefs and theories, but it opens up more ideas for scientists to work on. Once scientists can prove a theory/model wrong, they have a less amount of choices to figure out which is the correct answer. The atomic model starts out simple and scientists are able to add components to it as time passes. 3) Personally, I believe Thomson's model was the most impactful because it was the first discovery of electrons. It is a big step closer to completing the atomic model even though we have not discovered the nucleus yet. Scientists have figured out positive and negative charged objects in the atoms.4) Rutherford’s Model was the first to accurately explain that protons and neutrons were in the nucleus of an atom, and electrons were on the outside edges of the atom. 5) 500 years can make a big difference in our science knowledge. I predict that scientists will find a way to classify atomic models into even more detailed specific groups. We never know what we may discover for "science is tentative".


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