Review of Atomic Theory

1. Review of Atomic Theory A powerpoint compiled by the best chemistry teacher ever, Mr Soltmann, and created by his first period honors chemistry class.

2. Democritus • Anicent Greek Philosopher • Made first Atomic Theory • Universe made of two elements - atoms, and the void in which they exist • Wrote books and encyclopedias • Plato dislikes his work in Little Cosmology • Was taught by Leucippus http://www.mlahanas.de/Greeks/Bios/DemocritusNaples.jpg

3. Leucippus • Relatively unknown • Born at Miletus or Abdera • Cotemporary of Zeno, Empedocles, and Anaxagoras • Credited with originating the theory of atomism • Taught Democritus • Fame overshadowed by student http://reich-chemistry.wikispaces.com/file/view/Leucippus.jpg/147027201/Leucippus.jpg

4. Aristotle • 384 - 322 BC • Born in Stagira • Taught by Plato, but opposed ideas • First tutored in Medicine, but switched to Philosophy with Plato • Worked with subjects like Biology, Physics, Morals, Aesthetics, and Politics. • Most considered to be incomplete works. http://mrsvesseymathematicians.wikispaces.com/file/view/aristotle_stone.jpg/122672537/aristotle_stone.jpg

5. Atomism • Leucippus originated Atomism • Everything is composed of unbreakable homogenous elements called atoms • Constantly in motion and through collisions and regroupings, formed various compounds through which everything was made • There are an infinite amount of atoms • Democritus theorized that all mater is composed of tiny units called Atoms. • They don’t change, but move in space to combine to form all objects • Characteristic of object determined by shape of object. For example ,sweet things are made of smooth atoms, bitter made from sharp http://www.detoxifynow.com/Images/atom1.jpg

6. Theory of Four Elements • Was developed by Geek philosopher by Empedocles • All matter (including atoms) made up of fire, earth, water, and air • Could constantly cut matter • Was accepted over the concept of Atomism • Did not believe in atomism • Aristotle believed in theory of four elements. • Influenced by thought of the existence of Greek Gods • Fire and Water are opposites, and Earth and Air were opposites • Each of the opposites was considered to have existed in ideal form apart from Earth, and a mixed, impure form away from Earth. http://reich-chemistry.wikispaces.com/file/view/ist2_700000_four_elements_vector.jpg/31319395/ist2_700000_four_elements_vector.jpg

7. Antoine Laurent Lavoisier and The Law of Conservation of Matter by: Ryan Hall and Ben Sherman.

8. Background Information • Born Antoine Laurent Lavoisier, he was known as the Father of Modern Chemistry, and sometimes Physics as well. • Born in Paris, France, on August 26th, 1743 • Received a large fortune at the age of five due to his mother's death. • Attended the Mazarin College in 1754 to 1761, studying chemistry, botany, astronomy, and mathematics. • In 1771, at the age of 28, he married Marie-Anne Pierrette Paulze, who was only 13 at the time. • Paulze proved to be very helpful, and was able to translate documents, create drawings of many laboratory experiments, and edit and publish Lavoisier's memoirs.  •  Paulze also hosted parties, where scientists discussed their new ideas.

9. Background Information • Lavoisier discovered the elements of oxygen and hydrogen, helped in the creation of the metric system, and wrote the first extensive list of elements. • He also discovered the importance of the role of oxygen in combustion, and that diamonds and graphite were both forms of the same element, carbon. • On May 8th, 1794, Lavoisier was tried for  defending foreign born scientists from having to forfeit their freedom and possessions in France. • Later that day, he was guillotined for being a traitor, dieing at the age of 50.

10. The Law Of Conservation of Matter • "During an ordinary chemical change, there is no detectable increase or decrease in the quantity of matter." • This law is also referred to as the law of conservation of mass • This means the mass of a substance before a reaction takes place is always the same as the mass of the reactants • For example: If you combine the reactants Iron and Sulfur (Fe+S), the product would still be made of iron and sulfur, just in a different chemical form. • After the reaction takes place, the mass of the iron and sulfur will be the same as that of the iron sulfide

11. The Law (contd.) • Originally, the Law of Conservation of Mass was not accepted in the world. • This was because, for example, when you would burn an item, it would weigh less after the reaction took place. • People had not realized that mass was lost through oxygen.  • Once reactions could be completed and weighed in a vacuum, the law could be successfully proved.  • When the gas was in a vacuum, it could not accidentally escape.   • Also, now that it is sealed in a container, the gas could now be weighed

12. Significance of Law of Conservation of Mass • This discovery of the Law of Conservation of Mass was an important step in changing alchemy to modern chemistry. • Because of this new knowledge, scientists had to go back and recheck their previous mass measurements that they took when they performed past experiments. • Many of these previously-taken measurements proved to be incorrect. • This law was the basis for many later scientific discoveries.  • Without this law, the Law of Conservation of Energy, another important scientific discovery, would not exist.

13. Significance of Law of Conservation of Mass • Nowadays, the Law of Conservation of Mass is common knowledge for all scientists. • The scientific society now understands how, during a reaction, matter only changes state, between being a solid, liquid, or gas. • Before this law was created, scientists didn't completely understand that gases were just another state of matter.  • They also hadn't tried performing reactions in sealed containers to determine whether gases were being consumed from or released into the air.  • Lavoisier's findings proved that they knew less than they thought

14. Joseph Proust (1754-1826) Proust was a renown French chemist of his time. He began studying chemistry in his father’s apothecary at a young age. His most famous hypothesis was the controversial idea of the Law of Definite Proportions.

15. Background Info (cont.) • He began his career as a pharmacist at the Salpêriére Hospital in Paris, France • He abandoned this position and entered the field of chemistry • He taught chemistry at the Musé, a private scientific institution in Paris • He also taught at the Chemistry School in Segovia, Spain

16. Law of Definite Proportions • He used inorganic binary compounds to test his hypothesis • Ex: metallic oxides, sulfides, sulfates • This hypothesis stated that chemical substances could only join together to form a small number of compounds • These compounds had components that combined in fixed proportions based on their weight

17. Law of Definite Proportions (cont.) • Pure compounds contain elements that combine in definite proportions to each other • For example: Oxygen will always be 8/9 the mass of pure water, while hydrogen will always be 1/9 the mass • This idea was published in 1795

18. Controversy of Proust’s Findings • Proust’s hypothesis was rejected by other chemists of his time • Claude Louis Berthollet, another French chemist, believed that elements could combine in any proportion • This shows that they had not yet discovered the difference between pure chemical compounds and mixtures

19. Impact on Modern Day Chemistry • Proust’s ideas helped contribute to the atomic theory constructed by John Dalton promoted in 1803 • Today, it has been proven that there are certain, rare exceptions to the Law of Definite Proportions • Ex: iron oxide wüstite

20. John Dalton • John Dalton (6 September 1766 - 27 July 1844) was an English chemist, meteorologist and physicist • Best known for his pioneering work in the development of modern atomic theory, and his research into color blindness.

21. John Dalton was born into a Quaker family at Eaglesfield in Cumberland, England. • Dalton's first publication was Meteorological Observations and Essays (1793), which contained the seeds of several of his later discoveries. • A second work by Dalton, Elements of English Grammar, was published in 1801.

22. Atomic theory • Is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity. • John Dalton did more experiments to prove this and soon found that he could use his theory and understanding of gases and the elements to find out the atomic weight of each element.

23. Elements are made of the smallest particles called atoms. • All atoms for a particular element are identical. • Atoms of different elements can be told apart by their atomic weight. • Atoms of different elements can combine in a chemical reaction to form chemical compounds in fixed ratios.

24. Law of multiple proportions • The law is based of The law of definite proportions • Is one of the fundamental laws and was first discovered by the John Dalton in 1803. • Dalton experimented with a gas called nitric oxide (NO) and oxygen (O). He reacted them together to produce a third type of gas. The results were determined by the proportions or ratios of the two reacting gasses.

25. The law states that when chemical elements combine, they do so in a ratio of small whole numbers. • If two elements form more than one compound between them, the ratios of the masses of the second element to a fixed mass of the first element will also be in small whole numbers.

26. JJ Thomson • Born on December 18, 1856 • Received a scholarship to one of the most prestigious colleges in England, Trinity College. • He received a BA in Math • He has one son named George and a daughter named Joan.

27. Preceding Chemistry Discoveries • Discovery of atoms

28. JJ Thomson • He is known for: • Plum pudding model • Discovery of electron • Discovery of isotopes • Mass spectrometer invention • First m/e measurement • Thomson (unit)

29. Cathode Ray • What is it? • A glass apparatus, evacuated tube • Has a partial vacuum • Negatively charged cathode • Positively charged anode

31. The Experiment • What happened? • Electricity passes through a tube from two electrodes • Through the cathode and anode • A current is created, which is called cathode ray • The ray goes from one side of the tube to the other • When this occurs a florescent spot and coating on the opposite side is shown.

32. The Experiment Continued... • What happened next? • An external magnetic field has an effect on the ray

33. The Results • This proved that the Cathode Ray has a mass and a negative charge. • This developed the mass to charge ratio of particle: m/q • He realized that the rays were particles that were smaller than the atom (he called these corpuscles) • Other scientists later proved that his findings were electrons, making him the first to discover this negatively charged particle.

34. The Results • The discovery lead to the Plum Pudding Model • Which then lead to the Bohr Model of the atom • His discoveries still effect modern ideas and technologies • Computer, Tv • - This started a whole new era of scientific discovery and greatly impacts all of our lives

35. Robert Milikan Caroline and Nick

36. HIS LIFE • He was born March 22, 1868 in Morrison Illinois. • He went to Oberlin college and then he got his doctorate in physics from Columbia. • Professor at University of Chicago • He became the Caltech President (California Institute of Technology)

37. HIS LIFE CONTINUED • He won the noble prize for finding the charge on an electron • Millikan has a middle school named after him in Los Angeles. It is known as Millikan Middle School. • He did work with the Photoelectric Effect • He died of heart attack on December 19, 1953.

38. The Oil Drop Experiment • The goal of this was to find the charge of an electron. • The experiment entailed balancing the downward gravitational force with the upward buoyant and electric forces on tiny charged droplets of oil suspended between two metal electrodes.

39. How Does It Work?

40. What Does This All Mean? • FOUND CHARGE OF ELECTRON!!!!!!!!!!!!!! • Millikan was able to determine the kinetic energy of the ejected electrons obey the formula Einstein proposed. (1/2mv2=hf-p) • First to measure the charge accurately!

41. What Does This All Mean? • His ingenious experiment displayed that a charge on a single electron was the smallest possible amount of charge. • He used his results to inspire himself to develop the value of Avogadro’s Number. (6.02 X 1023 ) AKA 1 Mole! • He proved the electric charge is quantized.

42. Not Getting The Big Picture? Video Aid

43. Rutherford Ernest • Born on August 30, 1871 in New Zealand • Went to college and graduated with a degree in Mathematics and Physical Science • He won scholarship allowing him to further his education at Trinity college, studying under scientist JJ Thompson • He is known as the Father of Nucelar Physics • Won the Nobel Prize for Chemistry in 1908 By: Caroline Gluck and Carly Saferstein

44. Rutherford Ernest • His experiments consisted of: • Developing terms “alpha” and “beta” to indicate two types of radiation and later a third type of radiation, gamma rays • Collaborating with Fredrick Soddy on changing an elements with radioactive decay • Discovered radioactivity could be used to determine the age of a substance (radioactive dating) such as the Earth By: Caroline Gluck and Carly Saferstein

45. BEFORE The Gold Foil Experiment • Before Rutherford’s experiment, the model of an atom was not properly understood and thought of as “plum pudding: • The negative charges were in small grouping throughout the atom surrounded by a “pool” of positive charges • His experiment led to the discovery of the atomic nucleolus By: Caroline Gluck and Carly Saferstein

46. The Gold Foil Experiment • The experiment shot a tiny, dense beam of positive alpha particles at thin metal foils • His hypothesis was that the bean would pass straight through the foil’s atoms without being deflected (changing direction) By: Caroline Gluck and Carly Saferstein

47. The Gold Foil Experiment • The experiment involved: • A block of radium inside a lead box • with a hole for the alpha to shoot out of • A thin gold foil to • interrupt the beam of • alpha particles • A circular florescent • screen detecting • alpha particle • beams By: Caroline Gluck and Carly Saferstein

48. The Gold Foil Experiment • The experiment involved: • The deflected beams were unexpected and did not fit • the hypothesis that expressed the properties of the “plum pudding” atomic model • He found that the alpha particles were being deflected by something small, dense and positive- the nucleus • His experiment led to the discovery of the atomic nucleolus By: Caroline Gluck and Carly Saferstein

49. The Gold Foil Experiment Significance • Rutherford proved the “Plum Pudding” atomic model wrong • Negatively charged groupings did not consist of large enough masses or charges to strongly deflect the alpha beam • Positive “pudding” did also not consist of large enough masses or charges to strongly deflect the alpha beam By: Caroline Gluck and Carly Saferstein

50. The Gold Foil Experiment Significance • Invented theory of the that much of atoms mass is in dense ball in the center, now known as the nucleolus • He proposed that outside of dense ball was mostly empty space • From his discovery, newer and more accurate models of the atom were able to be created By: Caroline Gluck and Carly Saferstein