PowerPoint Slides Shown Friday, Oct. 03 2008

1. PowerPoint Slides Shown Friday, Oct. 03 2008 CH142B

2. •HOMEWORK #1 ON WEBASSIGN: DUE DATE FRIDAY OCT. 10 AT 11:59 PM•”MISSED” QUIZ SECTION

3. A cathode-ray tube. The fast-moving electrons

4. Deflection of cathode rays by an applied electric field.

5. J. J. Thompson got the charge-to-mass ratio for the electron e/me = -1.76 x 108 C/g

6. Thomson’s PlumPudding model

7. Schematic representation of the apparatus used by Millikan

9. What Millikan found was that all the charges on the oil droplets were multiples of 1.60 x 10-19 CThis must be the charge on the electron!

10. Mullikan got the charge on the electron: -1.60 x 10-19 C-1.60 x 10-19 C is defined as 1 electrostatic unit (esu) So me = 9.11 x 10-31 kg

11. 1 atomic mass unit (amu) = 1.66054 x 10-27 kg6.022 x 1023 amu =1 g  Exact Number

12. Rutherford Experiment • Alpha particles bombarding the atom. • Rationale - to study the internal structure of the atom, and to know more about the mass distribution in the atom! • Bombarded a thin Gold foil with Alpha particles from Radium.

13. Rutherford’s experiment

14. The expected results of the metal foil experiment

15. Ernest Rutherford (1871-1937) • Won the Nobel Prize in Chemistry in 1908 • “It was quite the most incredible event..... It was almost as if a gunner were to fire a shell at a piece of tissue and the shell bounced right back!!!!! ”

16. Nuclear atom cross section

17. The Masses and Charges of the Electron Proton and Neutron Particle Mass Charge* Electron 9.11 x 10 –31 kg (5.485 x 10-4 amu) -1 Proton 1.67 x 10 – 27 kg (1.0073 amu) +1 Neutron 1.67 x 10 – 27 kg (1.0087 amu) 0 *In esu

18. Atomic Definitions I: Symbols, Isotopes,Numbers A X The Nuclear Symbol of the Atom, or Isotope Z X = Atomic symbol of the element, or element symbol A = The Mass number; A = Z + N Z = The Atomic Number, the Number of Protons in the Nucleus N = The Number of Neutrons in the Nucleus Isotopes = atoms of an element with the same number of protons, but different numbers of Neutrons in the Nucleus

19. Modern Reassessment of the Atomic Theory 1. All matter is composed of atoms. Although atoms are composed of smaller particles (electrons, protons, and neutrons), the atom is the smallest body thatretains the unique identity of the element. 2. Atoms of one element cannot be converted into atoms of another element ina chemical reaction. Elements can only be converted into other elements in Nuclear reactions in which protons are changed. 3. All atoms of an element have the same number of protons and electrons, which determines the chemical behavior of the element. Isotopes of an element differ in the number of neutrons, and thus in mass number, but a sample of the element is treated as though its atoms have an average mass. 4. Compounds are formed by the chemical combination of two or more elements in specific ratios, as originally stated by Dalton.

20. Isotopes of Sodium

22. Neutral ATOMS • 51 Cr = P+ (24), e- (24), • N (27) • 239 Pu = P+(94), e- (94), • N (145) • 15 N = P+(7), e-(7), N(8) • 56 Fe = P+(26), e-(26), • N (30) • 235 U =P+(92), e-(92), • N (143)

23. Cations and Anions Cations: Possess a positive charge; they have lost one or more electrons. Anions: Possess a negative charge; they have gained one or more electrons. Charge is shown here A C X Z

24. 51 Cr+3 = P+ (24), e- (21), • N (27) • 239 Pu+5 = P+(94), e- (89), • N (145) • 15 N-3 = P+(7), e-(10), N(8) • 56 Fe+2 = P+(26), e-(24), • N (30) • 235 U+6 =P+(92), e-(86), • N (143) • 51 Cr = P+ (24), e- (24), • N (27) • 239 Pu = P+(94), e- (94), • N (145) • 15 N = P+(7), e-(7), N(8) • 56 Fe = P+(26), e-(26), • N (30) • 235 U =P+(92), e-(92), • N (143)

25. The terms also apply to polyatomic species OH- possesses 10 total electrons = 1 from H + 8 from O + 1 extra CH3+ possesses 8 total electrons = 3 from 3 H’s (1 each) + 6 from C - 1 PO4-3 possesses 50 total electrons = 15 from P + 8(4) from O + 3

26. Definitions for Components of Matter Pure Substances - Their compositions are fixed! Elements and compounds are examples of Pure Substances. Element - Is the simplest type of substance with unique physical and chemical properties. An element consists of only one type of atom. It cannot be broken down into any simpler substances by physical or chemical means. Molecule - Is a structure that is consisting of two or more atoms that are chemically bound together and thus behaves as an independent unit. Compound - Is a substance composed of two or more elements that are chemically combined. Mixture - Is a group of two or more elements and/or compounds that are physically intermingled.

27. AxByCzDw

28. Chemical Formulas Empirical Formula- Shows the relative number of atoms of each element in the compound. It is the simplest formula, and is derived from masses of the elements. Molecular Formula - Shows the actual number of atoms of each element in the molecule of the compound. Structural Formula - Shows the actual number of atoms, and the bonds between them ; that is, the arrangement of atoms in the molecule.

29. Definitions Chemical Bonds – The forces that hold atoms together in compounds Covalent Bonds – The sharing of electrons in a chemical bond Molecule – A group of atoms held together by covalent bonds Chemical Formula – The symbols of for the elements are used to indicate the types of atoms present, and the subscripts are used to indicate the relative numbers of atoms present Structural Formula – a Formula in which the bonds are shown along with the elemental symbols and order of atom arrangement