Chemistry Chapter 3

1. Chemistry Chapter3 Atoms: The Building Blocks of Matter

2. Clicker ? How long have people been interested in understanding matter and its structure? • Thousands of years • Hundreds of years • A few years • Never

3. Ancient Philosophy Who:Aristotle, Democritus When: More than 2000 years ago Where: Greece What: Aristotle believed in 4 elements: Earth, Air, Fire, and Water. Democritus believed that matter was made of small particles he named “atoms”. Why: Aristotle and Democritus used observation and inferrence to explain the existence of everything.

4. Alchemists Who:European Scientists When: 800 – 900 years ago Where: Europe What: Their work developed into what is now modern chemistry. Why: Trying to change ordinary materials into gold.

5. Particle Theory

6. Dalton(1800’s) Proposed the law of simple and multiple proportions Atoms of elements are the same and have the same mass Compounds have atoms of different elements combined together Atoms of different elements are different and have different masses First table that included the masses of atoms

7. John Dalton Above: John Dalton Right: His table of elements

8. Particle Theory Who:John Dalton When: 1808 Where: England What: Described atoms as tiny particles that could not be divided. Thought each element was made of its own kind of atom. Why: Building on the ideas of Democritus in ancient Greece.

9. Henri Becquerel By: Iwan & Sammy

10. About him • Born in Paris on December 15, 1852. • Born into 4 generations of scientists. • Studied at EcolePolytechnique. • Later married Louise Lorieux.

11. What he did • Discovered phosphorescence in uranium salts. • Experimented with radiation by taking a photographic plate and covering it with black paper and observing the reactions.

12. Particle Theory Who:Henri Becquerel When: 1896 Where: France What: Discovered radioactivity, the spontaneous emission of radiation by a material Why: Interested in fluorescence and phosphorescence

13. Discovery of Electrons

14. Joseph John Thomson By: Matthew Paulley Alex Strickland Blake Noell

15. Background • Born in Cheetham Hill on December 18, 1856 and died in 1940. • Discovered the electron in 1897 using experiments designed to study the nature of electric discharge. • Physics mentor. • Attended Owens College which had a great science faculty. • http://www.chemheritage.org/classroom/chemach/atomic/thomson.html

16. What He Accomplished and How • Treatise on the Motion of Vortex Ringswon him the Adams prize in 1884. • He studied Cathode Rays to reach the highest point of degree (culminating) to discover the electron. • Won the Noble Prize in Physics in 1906 because the discovery of the electron. • In 1986 he visited America to give lectures of his current researches. • http://nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-bio.html

18. Discovery of Electrons Who:J. J. Thompson When: 1897 Where: England What: Thompson discovered that electrons were smaller particles of an atom and were negatively charged. Why:Thompson knew atoms were neutrally charged, but couldn’t find the negative particle.

19. Millikan By Daniel, Jonathan, and Diego

20. What Did he do? • Robert Millikan discovered the charge on a electron. • He discovered this in 1910 • He discovered this with the falling drop method.

21. Pictures of Millikan

22. More pictures of Millikan

23. Discovery of Electrons Who:R.A. Milikan When: 1909 Where: USA What: In his oil drop experiment, determined the charge and the mass of an electron.  Why:Wanted to find the negatively charged particles in an atom

24. Atomic Structure I

25. Atomic Structure I Who: Ernest Rutherford When: 1911 Where: England What: Conducted an experiment to isolate the positive particles in an atom. Decided that the atoms were mostly empty space, but had a dense central core. Why: He knew that atoms had positive and negative particles, but could not decide how they were arranged.

26. Ernest Rutherford

27. Atomic Structure II

28. Niels Bohr Proposed a new theory of Ernest Rutherford’s Hydrogen Atom model.

29. 1915 • New theory of a hydrogen atom structure. • This is when he discovered that electrons can jump between orbits in an atom. • Because of this it caused radiation.

30. Atom

31. Atomic Structure II Who: Niels Bohr When: 1913 Where: England What: Proposed that electrons traveled in fixed paths around the nucleus. Scientists still use the Bohr model to show the number of electrons in each orbit around the nucleus. Why: Bohr was trying to show why the negative electrons were not sucked into the nucleus of the atom.

32. Wave Nature of Atoms

33. Erwin Schrödinger Thomas Parris, Matthew Gurak, Ty Adcock

34. 1935 • Schrodinger’s cat is a thought experiment • A cat was placed into a steel chamber along with a very small radioactive substance • If the radioactive substance decays it triggers a poison to be released • The scientist does not know whether the cat is dead until the box is opened, therefore the cat must be thought to be alive and dead at the same time

35. Atomic Model and Formula The Electron Cloud Formula Used

36. Describes how the quantum state of a physical system changes in time. • The Schrödinger equation describes time in a way that is inconvenient for relativistic theories.

37. Atomic Structure II Who: Erwin Schrödinger When: 1930 Where: Austria What: Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. Why: He was dissatisfied with the quantum condition in Bohr's orbit theory and he believed that atomic spectra should really be determined by some kind of equation.

38. The Neutron

39. James Chadwick By: Kaci Wages, Kayla Kittle, and Megan Morrow

40. Information on Chadwick • Born in Chesire, England on October 20, 1891. Died in 1974 • In 1935, he received the Nobel Peace Prize for physics for “possible existence of neutrons”. • Prisoner of War in Germany for 4 years • Co-author of Radiation from Radioactive Substances. Published in 1930

41. Chadwick’s Discovery • He was the leading advocate for creating the Atomic bomb in Britain. • Using alpha particles he discovered a neutral atomic particle with a mass close to a proton, which he named the neutron.

42. Chadwick’s Experiments • He performed tests on a new type of Radiation. • He smashed beryllium particles, a rare metallic element, and allowed the radiation that was released to hit another target • When the beryllium radiation hit hydrogen atoms in the wax, the atoms were sent into a detecting chamber. • Chadwick’s later experiments with particle accelerators contributed to the invention of the nuclear fisson bomb.

43. Atomic Model • He discovered the neutron part of the atom. It has no charge but has the same mass of a proton. • The model contains the nucleus which holds the protons & neutrons, and is orbited by the negative charged electrons.

44. The Neutron Who: James Chadwick When: 1932 Where: England What: Discovered the neutrally charged part of the atom – the neutron. Why: Wanted to determine why atoms were heavier than the protons and electrons combined.

45. Electron Cloud Model Electrons travel around the nucleus in random orbits. Scientists cannot predict where they will be at any given moment. Electrons travel so fast, they appear to form a “cloud” around the nucleus.

46. Electron Cloud Model