Outline
• Describe the basic structure of an atom• Recognize the importance of electrons • Understand isotopes and radioactivity• Describe chemical bonds and why they form• Be aware of the properties of water• Understand pH and buffers
Mass Number
+
+
– –
+
–
2
2
2
Protons
Neutrons
Electrons
Massnumber = 4
+
+
2e–
Electroncloud
NucleusHelium atom
Mass Number
+
–
6
6
6
Protons
Neutrons
Electrons
Massnumber = 12
+ +
6e–
Nucleus
Electroncloud
Carbon atom
1
H
3
Li4
Be
19
K
12Mg
93
Np94
Pu95
Am96
Cm97
Bk98
Cf99
Es100
Fm101
Md102
No103
Lr
37
Rb38
Sr39
Y42
Mo45
Rh46
Pd47
Ag48
Cd49
In50
Sn51
Sb52
Te53
I54
Xe
21
Sc40
Zr
22
Ti23
V24
Cr25
Mn27
Co28
Ni29
Cu30
Zn36
Kr
5
B6 C
8
O 2
He
55
Cs56
Ba72
Hf73
Ta74
W75
Re76
Os77
Ir78
Pt79
Au80
Hg81
Tl82
Pb83
Bi84
Po85
At86
Rn87
Fr88
Ra
57
La89
Ac104 105 106 107 108 109
58
Ce59
Pr60
Nd61
Pm62
Sm63
Eu64
Gd65
Tb66
Dy67
Ho68
Er69
Tm70
Yb71
Lu
90
Th91
Pa92
U
11
Na20Ca
41
Nb43
Tc44
Ru
26Fe
13
Al31
Ga32
Ge
14
Si7
N15P33
As
16
S35
Br34
Se
9
F18
Ar
10
Ne17
Cl
110
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Frequency of Elements in the Earth’s Crust
Radioactivity
Beta – neutron decay to loss of electron
Alpha – loss of two neutrons and two protons
Gamma – loss of energy
Radioactive Dating
Radioactive isotope half life
C-14 5730 years
H-3 12.25 years
U-238 4.5 billion years
Energy from different sources
Source Energy (MJ/kg)
Firewood 16
Coal 9-30
Natural Gas 39
Crude oil 45
Uranium (nuclear fission)
500,000
Summary of Isotopes92 naturally occurring elements
270 stable isotopes
50 natural radioisotopes
1000’s artificial isotopes
RadioactivityNuclear in origin
Releases energy energy (alpha, beta, gamma)
Uses: Energy, Dating Materials, Research & Medicine
Energylevel
3
+
–
+ +++
+ +MLK
Energylevel
2
Energylevel
1
Energylevel
1
Energylevel
2
Energylevel
3
–
M L K
Energy released
Ene
rgy
abso
rbed
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Energy Levels or Electron Shells
Energy Levels (Electron Shells)
Hydrogen (H)Atomic number = 1
Carbon (C)Atomic number = 6
Nitrogen (N)Atomic number = 7
Oxygen (O)Atomic number = 8
Outermost electron shell holds 8 electrons
First electron shell holds 2 electrons
Electron
Nucleus
Periodic Table Groups & Valence Electrons
Group 1 2 3 4 5 6 7 8
OuterEnergyElectrons 1 2 3 4 5 6 7 8
Outermost energy level
Electrons increase in #
Energy Levels
Increase
Fig. 2.15(TE Art)Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Properties of Water
Cohesion Adhesion
WatermoleculesSalt
crystal
Na+
Cl–
Cl–
Na+
Na+
Na+
Cl–
Cl–
Fig. 2.17(TE Art)Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Properties of Water
Solvent forms
Hydration Shells