2. CHAPTER 3: Elements and The Periodic Table Section 1 Structure of the Atom

3. The History of the Atom Democtritus 2000+ years ago (Atomos)

4. 2000+ years ago Democritis, a Greek philosopher Democritis, a Greek philosopher Said that everything was made up of tiny indivisible bodies called atoms. Said that everything was made up of tiny indivisible bodies called atoms. He named the atom from the word “atomos,” meaning not divisible. He named the atom from the word “atomos,” meaning not divisible.

5. 1803 John Dalton John Dalton Atoms are tiny round particles that cannot be divided. Atoms are tiny round particles that cannot be divided. Atoms of the same element are identical and have the same mass. Atoms of the same element are identical and have the same mass.

6. Dalton’s Model

7. 1897 J.J. Thompson J.J. Thompson Discovered electrons using a cathode ray tube. Discovered electrons using a cathode ray tube. Developed the “Plum Pudding” model of the atom. Developed the “Plum Pudding” model of the atom.

9. Thompson’s Plum Pudding Model

10. 1909-1911 Ernest Rutherford Ernest Rutherford Discovered the nucleus of an atom using gold foil and alpha particles. Discovered the nucleus of an atom using gold foil and alpha particles. Developed the “Solar System” model of the atom. Developed the “Solar System” model of the atom.

11. Rutherford’s Gold Foil Experiment

12. Gold Foil Experiment Results Click HERE!

13. Rutherford’s Solar System Model

14. 1914 Neils Bohr Neils Bohr Revised the “Solar System” model of the atom. Revised the “Solar System” model of the atom. Said that electrons travel in orbits around the nucleus. Said that electrons travel in orbits around the nucleus. Electrons lose energy when they move to a lower orbit, and gain energy when they move to a higher orbit. Electrons lose energy when they move to a lower orbit, and gain energy when they move to a higher orbit.

15. Bohr’s Revised Model

16. 1938 Erwin Schrödinger Erwin Schrödinger Developed “Electron Cloud” model of the atom. Developed “Electron Cloud” model of the atom. Said that electrons do not move in perfect circles, but still surround the nucleus. Said that electrons do not move in perfect circles, but still surround the nucleus. His model shows a probability of where an electron might be. His model shows a probability of where an electron might be.

17. Schrödinger’s Electron Cloud Model

20. The Structure of an Atom

22. Particles in an Atom Particle Relative Mass Charge Location in Atom Proton Neutron Electron 1 1 0 1+ none 1- Part of nucleus Moves around nucleus

23. # of Protons = Atomic number # of Electrons = # of protons # of Neutrons = mass number – atomic # (atomic mass rounded to nearest whole number)

24. How to Draw and Atom We already know that protons and neutrons are in the nucleus (the center) of the atom. We already know that protons and neutrons are in the nucleus (the center) of the atom. How do we know where to put the electrons around the nucleus? How do we know where to put the electrons around the nucleus? ENERGY LEVELS!

26. # of Electrons in Each Energy Level Energy Level Max # of Electrons 12 28 3 4 5 Maximum # of Electrons = 2n 2 (n = energy level) 18 32 50

27. Let’s draw an atom!

30. Now you try!

31. Questions from Yesterday... Can we see atoms? http://science.howstuffworks.com/atom9.htm Can we see atoms? http://science.howstuffworks.com/atom9.htm http://science.howstuffworks.com/atom9.htm How many atoms are in a cell? http://www.madsci.org/posts/archives/jun99/927 642230.Cb.r.html How many atoms are in a cell? http://www.madsci.org/posts/archives/jun99/927 642230.Cb.r.html http://www.madsci.org/posts/archives/jun99/927 642230.Cb.r.html http://www.madsci.org/posts/archives/jun99/927 642230.Cb.r.html If we really can’t see an atom, how do we know what it is made of? http://education.jlab.org/qa/history_04.html If we really can’t see an atom, how do we know what it is made of? http://education.jlab.org/qa/history_04.html http://education.jlab.org/qa/history_04.html

32. SMASH SOME ATOMS! Now it’s time to...

33. Why should we smash atoms? First, smashing atoms helps to get out your frustrations...well, not really. First, smashing atoms helps to get out your frustrations...well, not really. Scientists at Fermilab in Illinois smash particles so they can “see” what protons and neutrons are made of. Scientists at Fermilab in Illinois smash particles so they can “see” what protons and neutrons are made of.

34. Welcome to Fermilab! The Tevatron particle accelerator is 4 miles long!

35. What does the Tevatron do? In circular accelerators like the Tevatron, particles travel in a vacuum around a circular track many times. Electromagnets keep the particles confined in a narrow beam. At each pass, the magnetic field is strengthened so that the particle beam accelerates with each consecutive pass. When the particles are at their highest or desired energy, a target is placed in the path of the beam, in or near the detectors. When the particle beam strikes a target, various detectors record the events -- the subatomic particles and radiation released.

36. In English, Please? In the Tevatron, particles travel around in giant circles while gaining energy from magnets. When the particles have enough energy and are traveling fast enough, the target is placed in the loop and the particles hit it. Detectors make pictures/diagrams of what the collision looked like.

37. For example... This is the end view and side view of a collision of two gold beams. This is the end view and side view of a collision of two gold beams.

38. What did Scientists find? After smashing atoms, protons, and neutrons, scientists discovered that protons and neutrons can be broken down into quarks. After smashing atoms, protons, and neutrons, scientists discovered that protons and neutrons can be broken down into quarks. There are 3 quarks in a proton and 3 quarks in a neutron. There are 3 quarks in a proton and 3 quarks in a neutron. Quarks can be broken down 5 more times into more quarks! Quarks can be broken down 5 more times into more quarks!

39. Here’s the Breakdown p+ n Quarks

40. Types of Quarks Just to show you, here are a few “illustrations” of the 6 types of quarks and their names. Just to show you, here are a few “illustrations” of the 6 types of quarks and their names.

41. What can we do with this? A type of particle accelerator is in almost every TV and computer monitor!

42. What can we do with this? Scientists are learning more about what is inside a proton! The proton consists of three valence quarks and a sea of gluons and quark-antiquark pairs.