Atomic theory

1. atomic theory Mr. Marquardt Liberty Senior High

2. Introduction Throughout history, Truth about the world around us has gone through change. New technologies, information, discoveries and theories increased our understanding of this intriguing planet. Change is the nature of science, It is ongoing, self correcting and a dynamic entity dependent upon the progress of society and technology.

3. Introduction continued Theories are Scientists best explanation of the world around them based on scientific information. Example theories are: Plate Tectonics Theory Evolutionary Theory Big Bang Theory Atomic Model Theory To illustrate the process of change over time we will be studying the Atomic Model Theory.

4. History of Science Truth by gods Mesopotamia/Egypt 1% of population 5000-3500 B.C. were the rulers. 99% of population were the slaves. Technologies that brought early civilization include writing, coins, sails, wheels, organized government, tools for agriculture and irrigation.

5. History of Science Truth by observations The Ancient Greeks Philosophers were not true 1700-300 B.C. scientist. Truth was by questioning, then by observing the natural world around them. The Greeks had highly developed ideas about nature. However, they were just ideas. The Greeks consequently did not believe it was necessary to investigate. Consequently, they never performed experiments to test their ideas.

6. History of Science Truth by observations The Ancient Greeks Philosophers were were 1700-300 B.C. arrogant. Truth was by questioning, then by observing the natural world around them. Incubator, earthquakes, earth centered universe, earth flat. Thales, Democritus, Hippocrates, Socrates, Plato, Aristotle, Alexander the Great, Socrates, Phidippides.

7. History of Science Truth by occult practices, mystery religions, and pleasure in brutality. The Roman Empire Science and technology was 100 B.C.- 400A.D. slow. Little incentive to develop labor-saving devices because they had plenty of slaves. Lever, catapult, earth centered universe, volume. Archamedes, Ptolemy, Galen, Hero.

8. History of Science Truth was lost. (except for Muslim and Arab world. The Medieval times, the dark ages. 400 A.D. - 1500 A.D. The barbarian tribes overran The dying Roman Empire. Little progress in technology. had plenty slaves. Alchemy, castles, cathredrals. Lords and ladies, Knights, Braveheart.

9. History of Science Truth by Experimentation. The Renaisance, (rebirth) 1500 A.D. + Great progress in science was made. Printing Press, telescope, sun centered universe, genetics, modern chemistry, the scientific method. Galileo, Sir Isaac Newton, Copernicus, Shakesphere, Leonardo Da Vinci, Robert Boyle.

11. History of the Atom Democritus - Greek - Developed first atomic theory. Broke clay pots down into smaller and smaller pieces and claimed there is a limit to how small an item can be broken down to. Democritus gave the name of �Atom� to these small pieces which mean �indivisible� in Greek. Everything else is empty space.

12. History of the Atom Plato - Greek - pupil of socrates. Developed platonic theory. Small pieces (atoms) are classified into 5 geometric shapes. Earth, Air, Fire, Water, Cosmos. Aristotle, a pupil of Plato and Plato himself were the truth for many years. Aristotle claimed that matter was continuous and called this substance �hyle.� This was accepted for hundreds of years.

13. History of the Atom Prousts - Substances always contain elements in the same ratio. No matter the size, or where it is found. Law of definite proportions. Lavoisier - Compounds are made up of 2 or more elements. In a closed system, a chemical reaction yields a constant mass. Law of conservation of matter. Gay-Lassac - Studied gas reactions. Discovered O2 and H2 makes water. Substances are always found in whole number fixed proportions. For example CO2 not CO1.5 H2O not H.3O

14. History of the Atom John Dalton -1807- 1st �modern� theory of the atom. The theory contains the following 2 main ideas: All elements (20 at the time) are made up of atoms. Each element�s atoms were identical to each other in mass and density. Atoms combine in set # ratios Atoms of one element are all alike chemically.

15. History of the Atom William Crooke - Developed tubes designed to study cathode rays. These invisible rays could move a wheel and produce a shadow. These movements show the rays are made up of particles (matter) so small we cannot see it. William Roentgen - Experimented with these cathrode ray tubes. Noticed chemically treated paper glowing from across the room. This after he covered the tube with black paper. He discovered the ____________________. Henry Becquerel - studied materials that glowed in the dark. (fluoresced) On a cloudy day he set urnanium (not exposed to the sun) in a drawer next to sealed film. Found that matter containing uranium exposed the sealed photographic film. Discovered Uranium rays or natural radiation. These rays were more powerful than x-rays. What are the name of these particles that scientist keep discovering? Pierre & Marie Currie - Discovered other radioactive materials and that radiation is a property of heavy elements.

16. History of the Atom JJ Thomson -1897- Plum Pudding Model. Experimented with �invisible� particles by using magnets with the cathrode ray tubes. These particles would deflected by a negative electric field. Thus the ray �invisible particles� have a negative charged particle �electrons- which were embedded into the positive atom. Like raisons in a muffin or plums in a pudding. Cathode rays are made up of two items I Energy - high energy electromagnetic radiation II particles - evidence - sharp edges in shadows - bent the particles

17. History of the Atom Ernest Rutherford -1911 Classified forms of radiation according to their penetrating abilities. H igh energy - gamma rays Negative particle - beta particle Positive particle - alpha particle Gold foil experiment - sent alpha particles through different metals. Most went through but a few bounced back. This led to the discovery of the nucleus. Rutherfords Atomic model illustrates a mostly empty space with a tiny nucleus with a positive charge. Negative electrons move around the nucleus like bees around a hive.

20. Robert Bunsen Found that when heated, different elements produced different colors in a flame

21. History of the Atom Niels Bohr -1913 Planetary atomic model Electrons only occupy well-defined orbits with fixed energy levels Discovered that electrons may absorb energy by jumping to higher energy levels and fall back to the original level or orbit. This release of energy is called a photon. This energy called a photon gives off light energy called spectrum lines. These lines are the fingerprints of the elements.

22. Niels Bohr (1913) Electrons �orbit� the nucleus somewhat like planets orbit the sun Planetary Model

23. History of the Atom Present - Charge-Cloud model The following scientist were some of the people who developed our modern day model of an atom. Louis De Broglie - Found light waves behave like particles, and particles behave like waves. Pluck a string of a guitar. Werner Heisenberg - Uncertainty principle - no way of knowing where the electron is or how fast it is going. So described the model and an electron cloud. Max Born - Can only calculate the probability of finding an electron and not their exact location. Can we calculate the location of a fan at any given moment? The blades seem to take up the whole volume of the space in which they turn.

24. de Broglie and Schr�dinger Propose that electrons move like wave thus the Wave-Mechanical Model

25. Werner Heisenberg No experiment can measure the position and momentum of a quantum particle simultaneously Heisenberg�s Uncertainty Principle

26. Modern View of the Atom Tiny nucleus surrounded by electron �cloud� Nucleus accounts for all of the mass Arrangement of electrons causes different chemical properties

27. Electron Cloud Model

28. Electron Cloud Model Note: Just as no map can equal a territory, no concept of an atom can possibly equal its nature. These models of the atom simply served as a way of thinking about them, though they contained limitations (all models do).