Unit 5 : Atomic Structure

1. Unit 5 : Atomic Structure

2. Dalton’s Atomic Theory(1803) • Elements are made up of tiny invisible particles called atoms. • Atoms of the same element are identical. Atoms of different elements are different. • Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. • Chemical reactions are rearrangement of atoms. Atoms are not created, destroyed, nor broken apart.

3. Experiments to determine what an atom was • J. J. Thomson- used Cathode ray tubes • Clip of Cathode Ray Tube

4. Voltage source Thomson’s Experiment - +

5. Voltage source Thomson’s Experiment - +

6. Voltage source Thomson’s Experiment - + • Passing an electric current makes a beam appear to move from the negative to the positive end.

7. Voltage source Thomson’s Experiment • By adding an electric field

8. Voltage source + - • By adding an electric field, he concluded that the particles were Positively charged Negatively charged Not charged Some negative and some positively charged

9. Spread out + charge Thomsom’s Model • Found the electron. • Couldn’t find positive (for a while). • Said the atom was like plum pudding (p. 101) (or Jello with fruit) • A bunch of positive stuff, with the electrons able to be removed.

10. Rutherford’s Experiment • Used _________to produce alpha particles. • Aimed alpha particles at gold foil by drilling hole in _______ container. • Since the mass is evenly distributed in gold atoms alpha particles should go straight through. • Used gold foil because it could be made atoms thin.

11. Rutherford’s Experiment • After watching video, label the parts of his set-up on your handout.

12. Florescent Screen Lead block Polonium Gold Foil Alpha Particle

13. What he expected

14. Because

15. Because, he thought the positive charge (and mass)was evenly distributed in the atom. (according to Thomson’s Model)

16. What he got

17. How he explained it + • Atom is mostly empty • Small dense, positive pieceat center. • Rutherford just concluded • that atoms have: • Electrons • Protons • Neutrons • a Nucleus

18. + How he explained it • Atom is mostly empty • Small dense, positive pieceat center. • Alpha particlesare deflected by it if they get close enough.

19. +

20. Modern View • The atom is mostly empty space. • Two regions • Nucleus- protons and neutrons. • Electron cloud- region where you might find an electron.

21. Sub-Division of an Atom • Atom has two parts: - space where electrons travel Electron Cloud - small, dense Center of atom Nucleus

22. Size of Atoms • Very small, drawing a line across a penny would cross over _______________ atoms • Diameter of 1 atom = 1x10-8 cm --or-- • 350,000 • 4 million • 63 million • 810 million 1 Angstrom (Å) -- or – 10 nanometers

23. Size of Atoms • Most of atom is electron cloud • Nucleus is a very tiny portion of atom • Ratio, If an atom were the size of a football stadium, the nucleus would be the size of a pea !

24. Sub-Atomic Particles • ELECTRONS: • Negatively charged • Rotate around nucleus • All electrons are identical • Mass: insignificant compared to nucleus-0

25. Sub-Atomic Particles • Protons: • Positively charged - same magnitude as e- • Located in nucleus • Mass: “heavy” compared to an electron • All protons are identical • If proton were 1 kg, electron would be 1 cg • Mass = 1 atomic mass unit (amu)

26. Sub-Atomic Particles • Neutrons: • Neutral - no charge • Located in nucleus • All neutrons are identical • Mass: same as proton ( 1 amu) • . Proton Neutron Electron 1 amu 1 amu 0 amu

27. 1 H 1.0079 What the Numbers on Periodic Table Tell us about the Atom Atomic Number • The number of Protons • Equal to the number of electrons if atom is neutral • Protons determine identity of Element • Number of Protons does not change

28. 1 H 1.0079 What the Numbers on Periodic Table Tell us about the Atom Atomic Mass

29. Mass Number: • The Mass of an Atom (NOT found on Pd Table) • Mass of an atom = mass of the nucleus • Determined by counting Protons & Neutrons • Mass Number = # of Protons + # of Neutrons Ex: Oxygen Ex: Beryllium # of protons = # of protons = 8 4 + + # of neutrons = # of neutrons = 8 5 Mass Number = Mass Number = 16 9

30. Your Turn: Mass Number Ex: Potassium # of protons = 19 + # of neutrons = 40 Mass Number = Enter the # of neutrons into your clicker

31. Your Turn: Mass Number Ex: Potassium # of protons = 19 + # of neutrons = 21 Mass Number = 40

32. More Examples O2- Ex: Oxygen Ex: Oxide ( ) # of protons = # of protons = 8 8 # of electrons = # of electrons = 8 10 # of neutrons = # of neutrons = 8 8 Mass Number = Mass Number = 16 16 How many neutrons and electrons ?

33. Your Turn: Number of Electrons Ex: Bromide (Br-) # of protons = 35 # of electrons = Complete the Chart # of neutrons = Mass Number = 79 How many protons, then enter the # of neutrons into your clicker?

34. Your Turn: Number of Electrons Ex: Bromide (Br-) # of protons = 35 # of electrons = # of neutrons = 44 Mass Number = 79 Enter the # of electrons.

35. Your Turn: Number of Electrons Ex: Bromide (Br-) # of protons = 35 # of electrons = 36 # of neutrons = 44 Mass Number = 79

36. Your Turn: Number of Electrons Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = Complete the Chart # of neutrons = 13 Mass Number = 25 Enter the # of neutrons in clicker

37. Your Turn: Number of Electrons Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = 10 # of neutrons = 13 Mass Number = 25 Enter the # of electrons in clicker

38. Welcome Back ! • Check Your Posted Grades • Look at 2nd Marking Pd CLC’s and Verify Total • Look at Separate CLC Gradesheet for 3rd MP • Pick up your “Clicker” and Log in. • Tell Your Lab Partner what “Mass Number” means • Enter in clicker the # of Neutrons that are in Mg-25

39. Welcome Back ! • Have you or your partner Log in to a nearby computer. • Ask your partner what “Atomic Number” means • Tell Your Lab Partner what “Mass Number” means • Enter in clicker the # of Neutrons that are in Mg-25

40. Warm-Up Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = 10 # of neutrons = 13 Mass Number = 25 Enter the # of electrons in clicker

41. Lesson Review • The _____ is the total mass of a single atom. • Atomic Mass • Mass Number • Atomic Number • Number of Protons

42. Lesson Review • The _____ is always equal to the number of protons. • Atomic Mass • Mass Number • Atomic Number • Number of Neutrons

43. Lesson Review • The _____ is equal to the number of protons and neutrons • Atomic Mass • Mass Number • Atomic Number • Number of Protons

44. Lesson Review • The _____ is the difference between the number of protons and the number of electrons • Number of Neutrons • Atomic Number • Mass Number • Charge

45. Time for Practice: • Log in to Moodle and go to the pHet Activity called “Build an Atom” • Choose Game at Level 4

46. Isotopes • Different “Varieties” of an Atom • Isotopes are atoms of the same element, but with different #’s of Neutrons. Therefore, they have different Mass #’s. • Isotopes are Chemically Identical • About 300 Stable Isotopes of the first 83 elements exist, plus several hundred more unstable isotopes

47. Isotopes of Hydrogen: What has to be the same for all three? What will be different? 1 proton 1 proton 1 proton 1 neutron 2 neutrons 0 neutrons 1 amu 2 amu’s 3 amu’s Mass #:

48. Mass Number Have you ever heard of “tritium” before? Isotopes of Hydrogen: Hydrogen-1 Hydrogen-2 Hydrogen-3 “Protium” “Deuterium” “Tritium” 1 proton 1 proton 1 proton 1 neutrons 2 neutrons 0 neutrons 1 amu 2 amu’s 3 amu’s Mass #:

50. Isotopes of Hydrogen: Hydrogen-1 Hydrogen-2 Hydrogen-3 “Protium” “Deuterium” “Tritium” 1 proton 1 proton 1 proton 1 neutrons 2 neutrons 0 neutrons 1 amu 2 amu’s 3 amu’s Mass #: