1. Unit 1: Structure of Matter
Sections: , 7, PES
Copyright © The McGraw-Hill Companies, Inc.  Permission required for reproduction or display.

2. Democritus
Greek era
All matter consists of very small, indivisible particles, which he named atomos

3. Law of conservation of mass
Lavoisier
Law of conservation of mass
16 X
8 Y +
8 X2Y

4. Proust
Law of definite proportions

5. Dalton’s Atomic Theory
1. Elements are composed of extremely small particles called atoms.
2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements.
3. Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction.
4. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.

6. Law of Multiple Proportions

8. Review of Concepts
The atoms of elements A (blue) and B (orange) form two compounds shown here. Do these compounds obey the law of multiple proportions?

9. The speed (u) of the wave = l x n
Maxwell
Properties of Waves
Wavelength (l) is the distance between identical points on successive waves.
Amplitude is the vertical distance from the midline of a wave to the peak or trough.
Frequency (n) is the number of waves that pass through a particular point in 1 second (Hz = 1 cycle/s).
The speed (u) of the wave = l x n

10. Review of Concept
Which of the waves shown has (a) the highest frequency (b) the longest wavelength (c) the greatest amplitude?

11. proposed that visible light consists of electromagnetic waves.
Electromagnetic radiation is the emission and transmission of energy in the form of electromagnetic waves.
Speed of light (c) in vacuum = 3.00 x 108 m/s
All electromagnetic radiation
l x n = c

12. Practice Exercise
7.1
What is the wavelength (in meters) of an electromagnetic wave whose frequency is 3.64x107 Hz?

14. Cathode Ray Tube J.J. Thomson, measured mass/charge of e-
(1906 Nobel Prize in Physics)

15. *video

16. (a) A cathode ray produced in a discharge tube traveling from the cathode (left) to the anode (right). The ray itself is invisible, but the fluorescence of a zinc sulfide coating on the glass causes it to appear green. (b) The cathode ray is bent downward when a bar magnet is brought toward it. (c) When the polarity of the magnet is reversed, the ray bends in the opposite direction.

17. Thomson’s Model

18. Types of Radioactivityα β ϒ
(uranium compound)

19. *video

20. Mystery #1, “Heated Solids Problem”
Plank
Mystery #1, “Heated Solids Problem”
When solids are heated, they emit electromagnetic radiation over a wide range of wavelengths.
Radiant energy emitted by an object at a certain temperature depends on its wavelength.
Energy (light) is emitted or absorbed in discrete units (quantum).
E = h x n
Planck’s constant (h)
h = 6.63 x J•s
E = hc / λ
Because ν = c/λ
h = 6.63 x J•s

21. Practice Exercise
7.2
The energy of a photon is 5.87x10-20 J. What is its wavelength (in nanometers) ?

22. Photon is a “particle” of light
Einstein
Mystery #2, “Photoelectric Effect” hn
Light has both:
wave nature
particle nature
KE e-
Photoelectric effect phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency (threshold frequency)
Photon is a “particle” of light

23. Review of Concept
A clean metal surface is irradiated with light of three different wavelengths λ1, λ2, and λ3. The kinetic energies of the ejected electrons are as follows: λ1: 2.9×10−20 J; λ2: aprox 0; λ3: 4.2×10−19 J. Which light has the shortest wavelength and which has the longest wavelength?

24. Thomson’s charge/mass of e- = -1.76 x 108 C/g
Millikan’s Experiment
Measured mass of e-
(1923 Nobel Prize in Physics)
e- charge = x C
Thomson’s charge/mass of e- = x 108 C/g
e- mass = 9.10 x g

25. *video

26. (1908 Nobel Prize in Chemistry)
Rutherford’s Experiment
(1908 Nobel Prize in Chemistry)
particle velocity ~ 1.4 x 107 m/s
(~5% speed of light)
atoms positive charge is concentrated in the nucleus
proton (p) has opposite (+) charge of electron (-)
mass of p is 1840 x mass of e- (1.67 x g)

27. *video

28. *video

29. Rutherford’s Model of the Atom
atomic radius ~ 100 pm = 1 x m
nuclear radius ~ 5 x 10-3 pm = 5 x m
“If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.”

30. Atomic Number, Mass Number, and Isotopes
Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei
Mass Number X A Z
Element Symbol
Atomic Number H 1
H (D) 2
H (T) 3 U
235 92
238

31. The Isotopes of Hydrogen

32. Practice Exercise
2.1
How many protons, neutrons, and electrons are in the following isotope of copper: Cu?
What is the atomic number of an element if one of its isotopes has 117 neutrons and a mass number of 195?
Which of the following two symbols provides more information? O or O. 63 17 8

34. *video

35. Line Emission Spectrum of Hydrogen Atoms
Energize the sample
Line Emission Spectrum of Hydrogen Atoms

37. n (principal quantum number) = 1,2,3,…
Bohr Model of
the Atom (1913)
e- can only have specific (quantized) energy values
light is emitted as e- moves from one energy level to a lower energy level
En = −RH
( ) 1 n2
n (principal quantum number) = 1,2,3,…
RH (Rydberg constant) = 2.18 x 10-18J

39. Bohr
Planetary Model
Emission spectrum of Hydrogen supports the notion that energy is quantized and PES gives further evidence that those energy levels are divided into subshells

40. E = hn
E = hn

42. ( ) ( ) ( ) Ephoton = DE = Ef - Ei 1 Ef = -RH n2 1 Ei = -RH n2 1
nf = 2
ni = 3
nf = 1
ni = 3
Ef = -RH
( ) 1 n2 f
Ei = -RH
( ) 1 n2 i
nf = 1
ni = 2 i f
DE = RH
( ) 1 n2

44. Practice Exercise
7.4
What is the wavelength of a photon (in nanometers) emitted during a transition from the ni = 6 state to the nf = 4 state in the hydrogen atom?

45. Review of Concept
Which transition in the hydrogen atom would would emit light of a shorter wavelength? (a) ni = 5 nf = 3 or (b) ni = 4 nf = 2

46. Photoelectron Spectroscopy
PES
Further evidence to support bohr model

49. Standing Waves

50. Why is e- energy quantized?
De Broglie (1924)
Why is e- energy quantized?
reasoned that e- is both particle and wave.
2pr = nl l = h mv
v = velocity of e-
m = mass of e-

51. Practice Exercise
7.5
Calculate the wavelength (in nanometers) of a H atom (mass = 1.674x10-27 kg) moving at 7.00x102 cm/s.

52. Heisenberg Uncertainty principle

53. Schrodinger Wave Equation
In 1926 Schrodinger wrote an equation that described both the particle and wave nature of the e-
Wave function (y) describes:
. energy of e- with a given y
. probability of finding e- in a volume of space y2
Schrodinger’s equation can only be
solved exactly for the hydrogen atom.
Must approximate its solution for
multi-electron systems.
y is a function of four numbers called
quantum numbers

54. Schrödinger
Quantum Mechanical Model

55. Principal quantum number n
distance of e- from the nucleus
n=1
n=2
n=3

56. Angular Momentum quantum number
Shape of the “volume” of space that the e- occupies
Where 90% of the
e- density is found
for the 1s orbital
Sublevels:
s orbital
p orbital
d orbital
f orbital

57. Magnetic quantum number
orientation of the orbital in space

58. s orbital (1 orientation: sphere)

59. p orbital (3 orientations: dumbbells)

60. d orbital (5 orientations: double dumbbells)

61. f orbital (7 orientations)

62. Electron Spin quantum number

63. Coulomb’s Law
The force between two charged particles is proportional to the magnitude of each of the two charges (q1 and q2) and inversely proportional to the square of the distance between them (r)
*The force is along the straight line joining them
*Combine equations 1 & 2, then solve for force:

64. ( ) Energy of orbitals in a single electron atom 1 En = -RH n2
Energy only depends on principal quantum number n
n=3
n=2
En = -RH
( ) 1 n2
n=1

65. Energy of orbitals in a multi-electron atom
Energy depends on energy level and orbital shape

66. Shielding Effect Why is the 2s orbital lower in energy than the 2p?
“shielding” reduces the electrostatic attraction
Energy difference also depends on orbital shape

67. Electron configuration is how the electrons are distributed among the various atomic orbitals in an atom.
number of electrons
in the orbital
1s1
principal quantum
number n
Sublevel (shape)
Orbital diagram
1s1 H

69. “Fill up” electrons in lowest energy orbitals (Aufbau principle)

70. Order of orbitals (filling) in multi-electron atom
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s

71. Outermost subshell being filled with electrons

72. Pauli exclusion principle - no two electrons in an atom
can have the same four quantum numbers.
Each seat is uniquely identified (E, R12, S8).
Each seat can hold only one individual at a time.
Existence (and energy) of electron in atom is described
by its unique wave function y.

73. Paramagnetic
Diamagnetic
unpaired electrons
all electrons paired 2p 2p

74. The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins (Hund’s rule).

75. Practice Exercise
Calculate the total number of electrons that can be present in the principal level for which n = 4.
An oxygen atom has a total of eight electrons. Write the ground state electron configuration and orbital diagram.
The ground-state electron configuration of an atom is 1s22s22p63s23p3. What is the same/different for the three 3p electrons?

77. Noble Gas Configuration
Ex: Aluminum e− configuration: 1s22s22p63s23p1 preceding noble gas is Ne: 1s22s22p6 noble gas configuration: [Ne] 3s23p1

78. Practice Exercise
Write the noble gas configuration and the noble gas orbital diagram for sulfur (S).
Identify the atom that has the following ground-state electron configuration: [Ar]4s23d6

79. Chadwick (1935 Noble Prize in Physics)
H atoms: 1 p; He atoms: 2 p
mass He/mass H should = 2
measured mass He/mass H = 4
a + 9Be
1n + 12C + energy
neutron (n) is neutral (charge = 0)
n mass ~ p mass = 1.67 x g

81. mass p ≈ mass n ≈ 1840 x mass e-