Chapter 4 Structure of the Atom

1. Chapter 4Structure of the Atom 4.1 Early Theories of Matter 4.2 Subatomic Particles & Nuclear Atom 4.2.5 Ultimate Structure of Matter – The Standard Model (Not in Book) 4.3 How Atoms Differ 4.4 Unstable Nuclei & Radioactive Decay

2. Beyond proton/neutron/electron Picture • Textbook, page 97 • “the three subatomic particles you have just learned about have since been found to have their own structures. That is, they contain sub-subatomic particles. … will not be covered … because it is not understood if or how they affect chemical behavior.”

3. Beyond proton/neutron/electron Picture • Yes boys and girls, this is where we leap off the deep end!

4. Beyond proton/neutron/electron Picture (not in book) • To understand nucleus and how some nuclear radiation processes occur, need to examine both structure of nucleons (proton, neutron) and forces acting at nuclear distances • The standard model of physics attempts to describe all known forces and elementary particles

5. Hadrons Leptons Forces Baryons Mesons Charged Neutrinos Gravity Strong Weak EM Quarks Anti-Quarks What Is Matter ? Matter is all the “stuff” around you! The big picture (from standard model): Matter

6. Particles Launch Realplayer video from Fermilab Site Produced by Fermilab atoms proton/neutron/electron quarks antimatter leptons wave/particle duality electron diffraction http://vmsstreamer1.fnal.gov/VMS/VideoNews/VN77-Particles.ram

7. Antimatter – Paul Dirac In 1928, wrote down equation which combined quantum theory (developed in 1920s by Schrodinger and Heisenberg) and special relativity (1900s, Einstein), to describe behavior of electron Equation could have two solutions, one for electron with positive energy, and one for electron with negative energy But in classical physics (and common sense!), energy of particle must always be a positive number! http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.html

8. Antimatter – Paul Dirac Dirac interpreted this to mean that for every particle that exists there is a corresponding antiparticle, exactly matching the particle but with opposite charge For electron, for instance, there should be an "antielectron" identical in every way but with a positive electric charge In Nobel Lecture, Dirac speculated on existence of completely new Universe made out of antimatter! http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.html

9. Paul Dirac

10. Antimatter – Carl Anderson 1932, young professor at Caltech, studied showers of cosmic particles in cloud chamber; saw track left by "something positively charged, and with the same mass as an electron" After nearly 1 year of effort and observation, decided tracks were actually antielectrons, each produced alongside an electron from impact of cosmic rays in cloud chamber Called antielectron "positron", for its positive charge. discovery gave Anderson the Nobel Prize in 1936 and proved existence of antiparticles as predicted by Dirac http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html

11. Antimatter – Carl Anderson Anderson's cloud chamber picture of cosmic radiation from 1932 showing for first time the existence of anti-electron Particle enters from bottom, strikes lead plate in middle and loses energy as can be seen from greater curvature of upper part of track http://www.aps.org/publications/apsnews/200408/history.cfm http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html

12. Antimatter http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html Anderson close to his cloud chamber

13. Quantum Mechanics & Antimatter Nobel Prize, 1933 Erwin Shrodinger (Berlin U, Germany), Paul Adrien Maurice Dirac (U Cambridge, UK) “for the discovery of new productive forms of atomic theory”

14. Antimatter Nobel Prize, 1936 Hess (Innsbruck U, Austria), Anderson (Caltech) Hess: for his discovery of cosmic radiation Anderson: for his discovery of the positron [first confirmation of the existence of antimatter]

15. Hadrons Leptons Forces Baryons Mesons Charged Neutrinos Gravity Strong Weak EM Quarks Anti-Quarks Matter & Forces from Standard Model Matter

16. Particles in Standard Model • Six leptons are all elementary particles – includes the electron • All other particles (hadrons) are composed of combinations of quarks (6 kinds) – isolated quarks are not permitted • Class of hadrons called baryons composed of 3 quarks – includes proton & neutron • Class of hadrons called mesonscomposed of 2 quarks (quark + anti-quark) “Ordinary” matter

17. Standard Model Launch “The Standard Model” (Running time 6:36) Launch QT Video (stream) from Web The Standard Model

18. Standard ModelFour Fundamental Forces • In order of decreasing strength: • Strong – binds nucleons • Electromagnetic – “opposites attract” • Weak – involved in radioactive decay (beta decay) • Gravity • Forces arise through exchange of a mediating field particle (a boson)

19. Four Fundamental Forces ?

20. Standard Model Basic Particles and Force Carriers All 6 quarks and 6 leptons have corresponding antiparticles with opposite charge Some particles are their own antiparticles

24. “Colors” Of Quarks Quarks are said to havecolors (thought of as charge but 3 types) Colors –blue,redandgreen 3 colors of quark are attracted together Antiquarks have cyan, magenta, yellow Works by exchange ofgluons: called strong force

25. Structure within Proton (with gluons – animation) Structure within Proton

28. S0 po L+ D- Do K- D+ W- p- p p+ D++ K0 K+ W h a t a j u n g l e !

29. Dimensions of Subatomic Particles

30. Structure Within the Atom If protons and neutrons were 10 cm across, then quarks and electrons would be < 0.1 mm in size and entire atom would be ~ 10 km across

31. Space is mostly “empty space”

32. Atoms > 99.999% empty space Electron Nucleus

33. Protons & Neutrons are > 99.999% empty space g u Proton u Quarks make up negligiblefraction of protons volume !! d

34. The Universe The universe and all the matter in it is almost allempty space !(YIKES)

35. Why does matter appear to be so rigid ? Forces, forces, forces !!!! Primarily strong and electromagnetic forces which give matter its solid structure Strong force  defines nuclear size Electromagnetic force  defines atomic size

36. Standard Model Development • Developed by careful analysis of high energy physics experiments (particle accelerators and colliders) • Lots of heavy thinking!

37. Standard Model Related Nobel Prizes 1948 Blackett (Victoria U, Manchester, UK) for his development of the Wilson cloud chamber method, and his discoveries therewith in the fields of nuclear physics and cosmic radiation

38. Standard Model Related Nobel Prizes 1949 Yukawa (Kyoto Imperial U, Japan) for his prediction of the existence of mesons on the basis of theoretical work on nuclear forces

39. Standard Model Related Nobel Prizes 1950 Powell (Bristol U, UK) for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method

40. Standard Model Related Nobel Prizes 1957 Yang (Institute for Advanced Study, Princeton), Lee (Columbia U) for their penetrating investigation of the so-called parity laws which has led to important discoveries regarding the elementary particles

41. Standard Model Related Nobel Prizes 1959 Segre, Chamberlain (both U Cal. Berkeley) for their discovery of the antiproton

42. Standard Model Related Nobel Prizes 1963 Wigner (Princeton), Goeppert-Mayer (U Cal. La Jolla), Jensen (U. Heidelberg, Ger.) Wigner: for his contributions to theory of atomic nucleus and elementary particles, particularly through discovery and application of fundamental symmetry principles Goeppert-Mayer, Jensen: for their discoveries concerning nuclear shell structure

43. Standard Model Related Nobel Prizes 1965 Tomonaga (Tokyo U. of Education), Schwinger (Harvard), Feynmann (Caltech) for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles

44. Standard Model Related Nobel Prizes 1969 Gell-Mann (Caltech) for his contributions and discoveries concerning the classification of elementary particles and their interactions Proposed new quantum property of particles he called "strangeness number." Found even more general characteristics that allowed him to sort particles into eight "families" - called this grouping the eightfold way, referring to Buddhist philosophy's eight attributes of right living. Found that eightfold way could best be explained by a particle, undiscovered as yet, with 3 parts (hadrons), each holding a fraction of a charge.[Named and predicted existence of quarks.]

45. Standard Model Related http://www.telesio-galilei.com/L%20P%20Horwitz%20Summary%20of%20Scientific%20Contributions.pdf Lawrence P. Horwitz Algebraic approach to quark model In 1964, there were many expositions on the “quark model" of hadronic physics at CERN, and Horwitz (then at U of Geneva) brought the question to Yuval Ne'eman whether these results could be explained in term of group theory rather than the very questionable dynamics of such strongly interacting systems. They succeeded (with N. Cabibbo) in developing a group theoretical model which was very successful, and later justified its structure in terms of the asymptotic forms proposed by Gell-Mann and his student Melosh. Ms. Simon’s Father

46. Standard Model Related Nobel Prizes 1976 Richter (Stanford Linear Accelerator Lab), Ting (MIT) for their pioneering work in the discovery of a heavy elementary particle of a new kind

47. Standard Model Related Nobel Prizes 1979 Glashow (Harvard), Salam (Imperial College London) & Weinberg (Harvard) Theory of the unified weak and electromagnetic interaction (Weinberg coined term “standard model”)

48. Standard Model Related Nobel Prizes 1984 Rubbia & van der Meer (both CERN, Geneva) Discovery of field particles W and Z, communicators of weak interaction

49. Standard Model Related Nobel Prizes 1988 Lederman (Fermilab, Batavia, IL), Schwartz (Digital Pathways Inc, Mountain View, CA), Steinberger (CERN, Geneva) for neutrino beam method and demonstration of doublet structure of leptons through discovery of muon neutrino

50. Standard Model Related Nobel Prizes 1990 Friedman (MIT), Kendall (MIT), Taylor (Stanford U) for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for development of the quark model in particle physics