The Structure of the Atom

1. The Structure of the Atom Chap. 4

2. I. History

3. I. History A. Early Greeks Explain matter with 4 ‘elements’

4. I. History A. Early Greeks 1. Air 2. Earth 3. Fire 4. Water Explain matter with 4 ‘elements’

5. I. History A. Early Greeks B. Democritus Greek philosopher who first introduced concept of ‘atomos’

6. I. History A. Early Greeks B. Democritus C. Alchemists Devoted to making precious metals from base metals

7. I. History A. Early Greeks B. Democritus C. Alchemists D. Dalton Formulated the ‘Atomic Theory of Matter’

8. Atomic Theory of Matter 1. All matter is made of . . .

9. Atomic Theory of Matter 1. All matter is made of . . . 2. Atoms cannot be . . .

10. Atomic Theory of Matter 1. All matter is made of . . . 2. Atoms cannot be . . . 3. Atoms of a given element . . .

11. Atomic Theory of Matter 1. All matter is made of . . . 2. Atoms cannot be . . . 3. Atoms of a given element . . . 4. Atoms of 2 different elements . .

12. Atomic Theory of Matter 1. All matter is made of . . . 2. Atoms cannot be . . . 3. Atoms of a given element . . . 4. Atoms of different elements . . . 5. In a chemical reaction atoms are

13. I. History • A. Early Greeks • B. Democritus • C. Alchemists • Dalton • Definition of Atom

14. Atom The smallest particle of an element that retains properties of that element.

15. II. Discoveries of atoms • J.J. Thomson – 1890s Used a cathode ray tube (CRT) to measure the charge:mass ratio of an electron

16. II. Discoveries of atoms • J.J. Thomson – 1890s • chg:mass = • 1.76 x 1011 C/kg

17. II. Discoveries of atoms • J.J. Thomson – 1890s • chg:mass = • 1.76 x 1011 C/kg • Discovery led to plum-pudding model

18. II. Discoveries of atoms • J.J. Thomson – 1890s • Robert Millikan - 1909 Measured the charge of an electron in his ‘oil drop’ exper.

19. II. Discoveries of atoms • J.J. Thomson – 1890s • Robert Millikan - 1909 • Charge = 1.6 x 10-19

20. II. Discoveries of atoms • J.J. Thomson – 1890s • Robert Millikan - 1909 • Rutherford - 1911 Discovered nucleus in gold-foil experiment

21. II. Discoveries of atoms • J.J. Thomson – 1890s • Robert Millikan - 1909 • Rutherford - 1911 • Fired alpha particles at thin metal sheet.

22. II. Discoveries of atoms • J.J. Thomson – 1890s • Robert Millikan - 1909 • Rutherford - 1911 • Fired alpha particles at thin metal sheet. • Expected them to go straight through, but some deflected.

23. II. Discoveries of atoms • J.J. Thomson – 1890s • Robert Millikan - 1909 • Rutherford - 1911 • Fired alpha particles at thin metal sheet. • Expected them to go straight through, but some deflected. • This led to nuclear model.

24. II. Discoveries of atoms • The atom

25. II. Discoveries of atoms • The atom • The electron was discovered first

26. II. Discoveries of atoms • The atom • The electron was discovered first • The proton was described by Rutherford

27. II. Discoveries of atoms • The atom • The electron was discovered first • The proton was described by Rutherford • The neutron was described by Chadwick

28. III. Representing Atoms What makes a carbon atom different from a nitrogen atom?

29. III. Representing Atoms • The atomic number

30. III. Representing Atoms • The atomic number • The number of protons

31. III. Representing Atoms • The atomic number • The number of protons • Written on the periodic table.

32. III. Representing Atoms • The atomic number • The number of protons • Written on the periodic table. • This will equal the number of electrons, too.

33. III. Representing Atoms • The atomic number • The mass number

34. III. Representing Atoms • The atomic number • The mass number • The number of protons + neutrons

35. III. Representing Atoms • The atomic number • The mass number • The number of protons + neutrons • Always a whole number

36. III. Representing Atoms • The atomic number • The mass number • Isotopes

37. III. Representing Atoms • The atomic number • The mass number • Isotopes • Atoms with the same number of protons, different number of neutrons

38. III. Representing Atoms • The atomic number • The mass number • Isotopes • Atoms with the same number of protons, different number of neutrons • Isotopes have same properties, but different masses

39. III. Representing Atoms • The atomic number • The mass number • Isotopes • Notation

40. Nuclide Symbol Notation Cl 37 17

41. Nuclide Symbol Notation Element symbol Cl 37 17

42. Nuclide Symbol Notation Cl 37 17 Atomic number

43. Nuclide Symbol Notation Mass number Cl 37 17

44. Self Check – Ex. 1 Write the nuclide symbols for elements with these particles: Nuclide #1 22 protons 24 neutrons Nuclide #2 22 protons 26 neutrons

45. Self Check – Ex. 2 How many protons, neutrons, and electrons are in this element? 95 Mo 42

46. Self Check – Ex. 3 How many protons, neutrons, and electrons are in this element? 40 K

47. IV. Mass of atoms

48. IV. Mass of atoms • Measured in amu

49. IV. Mass of atoms • Measured in amu • Protons and neutrons both weigh about 1 amu (neutrons are a bit more)

50. IV. Mass of atoms • Measured in amu • Protons and neutrons both weigh about 1 amu (neutrons are a bit more) • The amu is defined as 1/12 the mass of carbon-12