1. Chapter 02 Lecture and Animation Outline
To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off.
Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click on the slide’s background before you can advance to the next slide.
See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes and animations. 1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. The Nature of Molecules and the Properties of Water
Chapter 2 2

3. Nature of Atoms Matter has mass and occupies space
All matter is composed of atoms
Understanding the structure of atoms is critical to understanding the nature of biological molecules 3

4. Atomic Structure Atoms are composed of Protons Neutrons Electrons
Positively charged particles
Located in the nucleus
Neutrons
Neutral particles
Electrons
Negatively charged particles
Found in orbitals surrounding the nucleus 4

5. a. b. Hydrogen Oxygen 1 Proton 1 Electron 8 Protons 8 Neutrons
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hydrogen
Oxygen
1 Proton
1 Electron
8 Protons
8 Neutrons
8 Electrons a. b.
proton
(positive charge)
electron
(negative charge)
neutron
(no charge) 5

6. Atomic number Number of protons equals number of electrons
Atoms are electrically neutral
Atomic number = number of protons
Every atom of a particular element has the same number of protons
Element
Any substance that cannot be broken down to any other substance by ordinary chemical means 6

7. Atomic mass Mass or weight?
Mass – refers to amount of substance
Weight – refers to force gravity exerts on substance
Sum of protons and neutrons is the atom’s atomic mass
Each proton and neutron has a mass of approximately 1 Dalton 7

8. Electrons Negatively charged particles located in orbitals
Neutral atoms have same number of electrons and protons
Ions are charged particles – unbalanced
Cation – more protons than electrons = net positive charge
Anion – fewer protons than electrons = net negative charge 8

9. Isotopes
Atoms of a single element that possess different numbers of neutrons
Radioactive isotopes are unstable and emit radiation as the nucleus breaks up
Half-life – time it takes for one-half of the atoms in a sample to decay 9

10. 10 Carbon-12 Carbon-13 Carbon-14 6 Protons 6 Neutrons 6 Electrons
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Carbon-12
Carbon-13
Carbon-14
6 Protons
6 Neutrons
6 Electrons
6 Protons
7 Neutrons
6 Electrons
6 Protons
8 Neutrons
6 Electrons 10

11. Electron arrangement
Key to the chemical behavior of an atom lies in the number and arrangement of its electrons in their orbitals
Bohr model – electrons in discrete orbits
Modern physics defines orbital as area around a nucleus where an electron is most likely to be found
No orbital can contain more than two electrons 11

12. Electron Shell Diagram Electron Shell Diagram Electron Shell Diagram
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Electron Shell Diagram
Corresponding Electron Orbital
Energy
Level K
One spherical orbital (1s)
Electron Shell Diagram
Corresponding Electron Orbitals y z
Energy
level L x
One spherical orbital (2s)
Three dumbbell-shaped orbitals (2kk)
Electron Shell Diagram
Electron Orbitals y z x 12
Neon

13. Energy levels
Electrons have potential energy related to their position
Electrons farther from nucleus have more energy
Be careful not to confuse energy levels, which are drawn as rings to indicate an electron’s energy, with orbitals, which have a variety of three-dimensional shapes and indicate an electron’s most likely location 13

14. 14 Energy Energy released absorbed Nucleus N K L M M L N K Nucleus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Energy
Energy
released
absorbed
Nucleus N K M L L M K N
Nucleus 14

15. Redox
During some chemical reactions, electrons can be transferred from one atom to another
Still retain the energy of their position in the atom
Oxidation = loss of an electron
Reduction = gain of an electron
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. + + + 15
Oxidation
Reduction

16. Elements
Periodic table displays elements according to valence electrons
Valence electrons – number of electrons in outermost energy level
Inert (nonreactive) elements have all eight electrons
Octet rule – atoms tend to establish completely full outer energy levels 16

17. Periodic Table of the Elements
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 8 H
Key O 2 C
Carbon (C) 1
atomic number He H 3 4
chemical symbol O
Oxygen (O) 5 6 C 9 Li Be 7 10 B F 14 N Ne Si H
Hydrogen (H) 11 12 13 15 Al 16 Na Mg P 17 18 S Cl Ar N
Nitrogen (N) 26 19 20 21 22 25 Fe Ca 23 24 27 28 29 30 31 32 33 34 35 36 K Ti Mn
Sodium (Na) Sc V Cr Co Ni Cu Zn Ga Ge As Se Br Kr Na 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Cl
Chlorine (Cl) Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Ca
Calcium (Ca) 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn P
Phosphorus (P) 87 88 89
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118 Fr Ra Ac Rf Ob Sg Bh Hs Mt Ds Rg Cn
Uut Fl
Uup Lv
Uus
Uuo K
Potassium (K) S
Sulfur (S) 58 59 60 61 62 63 64 65 66 67 68 69 70 71
(Lanthanide series) Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu F e
Iron (Fe) Mg
Magnesium (Mg) 90 91 92 93 94 95 96 97 98 99
100
101
102
103
(Actinide series) Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr a. b. 17

18. 90 naturally occurring elements
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
90 naturally occurring elements
Only 12 elements are found in living organisms in substantial amounts
Four elements make up 96.3% of human body weight
Carbon, hydrogen, oxygen, nitrogen
Organic molecules contain primarily CHON
Some trace elements are very important C
Carbon (C) O
Oxygen (O) H
Hydrogen (H) N
Nitrogen (N) Na
Sodium (Na) Cl
Chlorine (Cl) Ca
Calcium (Ca) P
Phosphorus (P) K
Potassium (K) S
Sulfur (S) Fe
Iron (Fe) Mg
Magnesium (Mg) b. 18

19. Chemical Bonds
Molecules are groups of atoms held together in a stable association
Compounds are molecules containing more than one type of element
Atoms are held together in molecules or compounds by chemical bonds 19

20. Ionic bonds Formed by the attraction of oppositely charged ions
Gain or loss of electrons forms ions
Na atom loses an electron to become Na+
Cl atom gains an electron to become Cl–
Opposite charges attract so that Na+ and Cl– remain associated as an ionic compound
Electrical attraction of water molecules can disrupt forces holding ions together 20

21. a. 21 b. NaCl crystal Na Na+ Sodium atom Sodium ion (+) Cl Cl–
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Na
Na+
Sodium atom
Sodium ion (+) Cl
Cl–
Chlorine atom
Chloride ion (–) a.
Cl–
Na+
Cl–
Na+
Cl–
Na+
Cl–
Na+
Cl– 21
b. NaCl crystal

22. Covalent bonds Form when atoms share 2 or more valence electrons
Results in no net charge, satisfies octet rule, no unpaired electrons
Strength of covalent bond depends on the number of shared electrons
Many biological compounds are composed of more than 2 atoms – may share electrons with 2 or more atoms 22

23. covalent bond Single covalent bond Hydrogen gas H H H H H2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
covalent bond
Single covalent bond
Hydrogen gas H H H H H2
Double covalent bond
oxygen gas O O O O O2
Triple covalent bond
Nitrogen gas N N N N N2 23

24. Electronegativity Atom’s affinity for electrons
Differences in electronegativity dictate how electrons are distributed in covalent bonds
Nonpolar covalent bonds = equal sharing of electrons
Polar covalent bonds = unequal sharing of electrons 24

25. Chemical reactions
Chemical reactions involve the formation or breaking of chemical bonds
Atoms shift from one molecule to another without any change in number or identity of atoms
Reactants = original molecules
Products = molecules resulting from reaction
6H2O + 6CO → C6H12O O2
reactants products 25

26. Extent of chemical reaction influenced by
Temperature
Concentration of reactants and products
Catalysts
Many reactions are reversible 26

27. Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at 27

28. Water Life is inextricably tied to water
Single most outstanding chemical property of water is its ability to form hydrogen bonds
Weak chemical associations that form between the partially negative O atoms and the partially positive H atoms of two water molecules
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 28
a. Solid
b. Liquid
c. Gas
a: © Glen Allison/Getty Images RF; b: © PhotoLink/Getty Images RF; c: © Jeff Vanuga/Corbis

29. Polarity of water
Within a water molecule, the bonds between oxygen and hydrogen are highly polar
Oxygen is much more electronegative than Hydrogen
Partial electrical charges develop
Oxygen is partially negative δ+
Hydrogen is partially positive δ– 29

30. a. b. c . 8p 8n Bohr Model Ball-and-Stick Model + 104.5 +
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Bohr Model
Ball-and-Stick Model
 + +
 –
 +
104.5 8p 8n
 +
 –
 – +
 –
 + a. b.
Space-Filling Model
 +
 –
 + c .

31. Hydrogen bonds
Cohesion – polarity of water allows water molecules to be attracted to one another
Attraction produces hydrogen bonds
Each individual bond is weak and transitory
Cumulative effects are enormous
Responsible for many of water’s important physical properties 31

32. Hydrogen atom Water molecule + – Hydrogen bond a. Oxygen atom
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hydrogen atom
Water molecule + –
Hydrogen bond a.
Oxygen atom
Hydrogen atom
Hydrogen bond + –
An organic molecule 32 b .
Oxygen atom

33. Adhesion – water molecules stick to other polar molecules by hydrogen bonding
Cohesion – water molecules stick to other water molecules by hydrogen bonding 33

34. Properties of water Water has a high specific heat
A large amount of energy is required to change the temperature of water
Water has a high heat of vaporization
The evaporation of water from a surface causes cooling of that surface
Solid water is less dense than liquid water
Bodies of water freeze from the top down 34

35.  –  – Na+ Water molecules  –  –  – Hydration shells Na+ Cl– + +
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 –
 –
Na+
Water molecules
 –
 –
 –
Hydration shells
Na+
Cl– + +
Cl– + + +
Salt crystal 35

36. 5. Water organizes nonpolar molecules
4. Water is a good solvent
Water dissolves polar molecules and ions
5. Water organizes nonpolar molecules
Hydrophilic “water-loving”
Hydrophobic “water-fearing”
Water causes hydrophobic molecules to aggregate or assume specific shapes
6. Water can form ions
H2O  OH– H+
hydroxide ion hydrogen ion 36

37. Acids and bases Pure water
[H+] of 10–7 mol/L
Considered to be neutral
Neither acidic nor basic
pH is the negative logarithm of hydrogen ion concentration of solution 37

38. Acids and Bases - pH Acid Base
Any substance that dissociates in water to increase the [H+] (and lower the pH)
The stronger an acid is, the more hydrogen ions it produces and the lower its pH
Base
Substance that combines with H+ dissolved in water, and thus lowers the [H+] 38

39. Stomach acid, lemon juice 10–3 3 Vinegar, cola, beer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hydrogen Ion
Concentration [H+]
pH Value
Examples of Solutions
100
Acidic
10–1 1
Hydrochloric acid
10–2 2
Stomach acid, lemon juice
10–3 3
Vinegar, cola, beer
10–4 4
Tomatoes
10–5 5
Black coffee
10–6 6
Urine
10–7
Pure water
10–8 8
Seawater
10–9 9
Baking soda
10–10 10
Great Salt Lake
10–11 11
Household ammonia
10–12 12
Household bleach
10–13 13
10–14 14
Basic
Sodium hydroxide 39

40. Buffers Substance that resists changes in pH Act by
Releasing hydrogen ions when a base is added
Absorbing hydrogen ions when acid is added
Overall effect of keeping [H+] relatively constant 40

41. 9 8 7 6 Buffering range 5 pH 4 3 2 1 1X 2X 3X 4X 5X
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9 8 7 6
Buffering range 5 pH 4 3 2 1 1X 2X 3X 4X 5X
Amount of base added 41

42. Most biological buffers consist of a pair of molecules, one an acid and one a base
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – + + +
Water
(H2O)
Carbon
dioxide
(CO2)
Carbonic
acid
(H2CO3)
Bicarbonate
ion
(HCO3–)
Hydrogen
ion
(H+) + + 42