1. Matter consists of chemical elements in pure form and in combinations called compounds
Organisms are composed of matter
Matter is anything that takes up space and has mass
Matter is made up of elements

2. Elements and Compounds
An element is a substance that cannot be broken down to other substances by chemical reactions
A compound is a substance consisting of two or more elements in a fixed ratio

3. Sodium
Chlorine
Sodium chloride

4. Essential Elements of Life
Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur
Trace elements are those required by an organism in minute quantities

5. Table 2-1

6. Nitrogen deficiency
Iodine deficiency

7. Subatomic Particles Atoms are composed of subatomic particles Neutrons
Protons
Electrons

8. Atomic Number and Atomic Mass
Atoms of the various elements differ in number of subatomic particles
Atomic Number
Mass Number
Neutron mass and proton mass are almost identical and are measured in daltons

9. Isotopes
Atoms of an element have the same number of protons but may differ in number of neutrons
Isotopes are two atoms of an element that differ in number of neutrons
Radioactive isotopes decay spontaneously, giving off particles and energy

10. Carbon Isotopes

11. Some applications of radioactive isotopes in biological research:
Dating fossils
Tracing atoms through metabolic processes
Diagnosing medical disorders

12. make DNA. One compound is labeled with 3H.
TECHNIQUE
Compounds including
radioactive tracer
(bright blue)
Incubators 1 2 3
10ºC
15ºC
20ºC
Human cells 4 5 6
25ºC
30ºC
35ºC 1
Human
cells are
incubated
with compounds used to
make DNA. One compound is
labeled with 3H. 7 8 9
40ºC
45ºC
50ºC
Figure 2.6 Radioactive tracers 2
The cells are
placed in test
tubes; their DNA is
isolated; and
unused labeled
compounds are
removed.
DNA (old and new)

13. RESULTS Optimum temperature for DNA synthesis 30 Counts per minute
(x 1,000) 20 10 10 20 30 40 50
Temperature (°C)

14. Cancerous
throat
tissue

15. The Energy Levels of Electrons
Potential energy is the energy that matter has because of its location or structure
The electrons of an atom differ in their amounts of potential energy
An electron’s state of potential energy is called its energy level, or electron shell

16. Electron Configuration and Chemical Properties
The chemical behavior of an atom is determined by the distribution of electrons in electron shells
The periodic table of the elements shows the electron distribution for each element

17. He Hydrogen 1H 2 4.00 Helium 2He First shell Lithium 3Li Beryllium 4Be
Atomic number
Helium
2He
First
shell
Atomic mass
Element symbol
Electron-shell
diagram
Lithium
3Li
Beryllium
4Be
Boron 5B
Carbon 6C
Nitrogen 7N
Oxygen 8O
Fluorine 9F
Neon
10Ne
Second
shell
Sodium
11Na
Magnesium
12Mg
Aluminum
12Al
Silicon
14Si
Phosphorus
15P
Sulfur
16S
Chlorine
17Cl
Argon
18Ar
Third
shell

18. Valence electrons are those in the outermost shell, or valence shell
The chemical behavior of an atom is mostly determined by the valence electrons
Elements with a full valence shell are chemically inert
Each electron shell consists of a specific number of orbitals

19. The formation and function of molecules depend on chemical bonding between atoms
Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms
These interactions usually result in atoms staying close together, held by attractions called chemical bonds

20. Covalent Bonds
A covalent bond is the sharing of a pair of valence electrons by two atoms
In a covalent bond, the shared electrons count as part of each atom’s valence shell

21. Hydrogen atoms (2 H)
Hydrogen
molecule (H2)

22. A molecule consists of two or more atoms held together by covalent bonds
A single covalent bond, or single bond, is the sharing of one pair of valence electrons
A double covalent bond, or double bond, is the sharing of two pairs of valence electrons
Covalent bonds can form between atoms of the same element or atoms of different elements

23. Number of Covalent bonds

24. Single
covalent bond
Double
covalent bond

25. Name and Molecular Formula Electron- distribution Diagram Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
(a) Hydrogen (H2)
Figure 2.12 Covalent bonding in four molecules

26. Name and Molecular Formula Electron- distribution Diagram Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
(b) Oxygen (O2)
Figure 2.12 Covalent bonding in four molecules

27. Name and Molecular Formula Electron- distribution Diagram Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
(c) Water (H2O)
Figure 2.12 Covalent bonding in four molecules

28. Name and Molecular Formula Electron- distribution Diagram Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
(d) Methane (CH4)
Figure 2.12 Covalent bonding in four molecules

29. Electronegativity is an atom’s attraction for the electrons in a covalent bond
The more electronegative an atom, the more strongly it pulls shared electrons toward itself

30. – O H H + +
H2O

31. In a nonpolar covalent bond, the atoms share the electron equally
In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally
Unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule

32. Nonpolar Covalent Bond-bond between 2 nonmetal atoms that have the same electronegativity and therefore have equal sharing of the bonding electron pair
Example: In H-H each H atom has an electronegativity value of 2.1, therefore the covalent bond between them is considered nonpolar

33. Polar Covalent Bond-bond between 2 nonmetal atoms that have different electronegativities and therefore have unequal sharing of the bonding electron pair
Example: In H-Cl, the electronegativity of the Cl atom is 3.0, while that of the H atom is 2.1

34. Covalent bonds can be nonpolar or polar

35. The result is a bond where the electron pair is displaced toward the more electronegative atom. This atom then obtains a partial-negative charge while the less electronegative atom has a partial-positive charge.
This separation of charge or bond dipole can be illustrated using an arrow with the arrowhead directed toward the more electronegative atom. The Greek letter delta indicates “partially”

37. Ionic Bonds
Atoms sometimes strip electrons from their bonding partners
An example is the transfer of an electron from sodium to chlorine
After the transfer of an electron, both atoms have charges
A charged atom (or molecule) is called an ion

38. Anion - negatively charged ion
Cation - positively charged ion
Cations and anions are involved in biological processes, such as muscle contraction
An ionic bond is an attraction between an anion and a cation

39. Sodium, potassium, and chloride ions are essential for this nerve cell to stimulate these muscle fibers

40. Sodium chloride (NaCl)
Sodium atom
Chlorine atom
Sodium ion
(a cation)
Chloride ion
(an anion)
Figure 2.14 Electron transfer and ionic bonding
Sodium chloride (NaCl)

41. Compounds formed by ionic bonds are called ionic compounds, or salts
Salts, such as sodium chloride (table salt), are often found in nature as crystals

42. Weak Chemical Bonds
Most of the strongest bonds in organisms are covalent bonds that form a cell’s molecules
Weak chemical bonds, such as ionic bonds and hydrogen bonds, are also important
Weak chemical bonds reinforce shapes of large molecules and help molecules adhere to each other

43. Hydrogen Bonds
A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom
While individually weak, hydrogen bonds are strong when present in large numbers
In living cells, the electronegative partners are usually oxygen or nitrogen atoms

44. Hydrogen bonding gives water properties that help make life possible on Earth
All organisms are made mostly of water and live in an environment dominated by water
Water molecules are polar, with the oxygen region having a partial negative charge (d−) and the hydrogen region a slight positive charge (d)
Two water molecules are held together by a hydrogen bond 44

45. – +
Water
(H2O) +
Hydrogen bond –
Ammonia
(NH3) + + +

47. Van der Waals Interactions
If electrons are distributed asymmetrically in molecules or atoms, they can result in “hot spots” of positive or negative charge
Van der Waals interactions are attractions between molecules that are close together as a result of these charges 47

48. Van der Waals interactions are individually weak and occur only when atoms and molecules are very close together
Collectively, such interactions can be strong, as between molecules of a gecko’s toe hairs and a wall surface 48

49. Figure 2.UN01 In-text figure, Van der Waals interactions, p. 2749

50. Biological molecules recognize and interact with each other with a specificity based on molecular shape
Molecules with similar shapes can have similar biological effects

51. (a) Structures of endorphin and morphine
Key
Carbon
Hydrogen
Nitrogen
Sulfur
Oxygen
Natural endorphin
Morphine
(a) Structures of endorphin and morphine
Natural
endorphin
Figure 2.14 A molecular mimic
Morphine
Endorphin
receptors
Brain cell
(b) Binding to endorphin receptors 51

52. Carbon
Nitrogen
Hydrogen
Sulfur
Natural
endorphin
Oxygen
Morphine
Structures of endorphin and morphine

53. Natural
endorphin
Morphine
Endorphin
receptors
Brain cell
Binding to endorphin receptors

54. Chemical reactions make and break chemical bonds
Chemical reactions lead to new arrangements of atoms
The starting molecules of a chemical reaction are called reactants
The final molecules of a chemical reaction are called products

55. 2 H2 O2
2 H2O
Reactants
Reaction
Products

56. Photosynthesis is an important chemical reaction
In photosynthesis, sunlight powers the conversion of CO2 and H20 to glucose (C6H12O6) and O2

58. Some chemical reactions go to completion: All reactants are converted to products
Most chemical reactions are reversible: Products of the forward reaction become reactants for the reverse reaction
Chemical equilibrium is reached when the forward and reverse reaction rates are equal

59. Animations and Videos The Chemical Basis of Life
Atomic Symbols, Atomic Numbers and Mass Numbers
Electron Arrangement
Electron Configurations
Chemical Bonds
Bond Formation
Atomic Structure and Ionic Bonding

60. Animations and Videos Ionic Bonds – 1 Ionic Bonds – 2
Covalent Bonds – 1
Covalent Bonds – 2
Transition State
Bozeman - Coupled Reactions
Chapter Quiz Questions – 1
Chapter Quiz Questions – 2

61. Based on the periodic table shown here, which elements will most likely form an ionic bond?
Na and Cl, and Li and F
C and O
N and O
Si and Cl
all of the above
Answer: A is the best choice.
This question should lead to a discussion of the basic concepts of electronegativity and types of bonds.

62. Based on the periodic table shown here, which elements will most likely form an ionic bond?
Na and Cl, and Li and F
C and O
N and O
Si and Cl
all of the above 62

63. Based on the periodic table shown here, which elements will most likely form a covalent bond?
Na and Cl
C and O
N and O
Si and Cl
H and H
Answer: E is the best choice.
This question should lead to a discussion of the basic concepts of electronegativity and types of bonds. One way to change this question would be to add C and H as a choice. This could be used to lead into a more detailed discussion. 63

64. Based on the periodic table shown here, which elements will most likely form a covalent bond?
Na and Cl
C and O
N and O
Si and Cl
H and H 64

65. Titanium has an atomic number of 22
Titanium has an atomic number of 22. How many protons, neutrons, and electrons are in an isotope of titanium with mass number of 48?
p  22, n  26, e  22
p  11, n  26, e  11
p  11, n  11, e  70
p  11, n  22, e  48
p  22, n  22, e  48
Answer: A is the best choice.
This question can lead to discussion of electron number and numbers of electrons in electron shells.

66. Titanium has an atomic number of 22
Titanium has an atomic number of 22. How many protons, neutrons, and electrons are in an isotope of titanium with mass number of 48?
p  22, n  26, e  22
p  11, n  26, e  11
p  11, n  11, e  70
p  11, n  22, e  48
p  22, n  22, e  48

67. H2O can be considered ______, but H2 can only be considered ______.
an isotope and a molecule; a molecule
an isotope and a molecule; an isotope
a compound and an isotope; a molecule
a molecule and a compound; a compound
a molecule and a compound; a molecule
Answer: E is the best choice. 67

68. H2O can be considered ______, but H2 can only be considered ______.
an isotope and a molecule; a molecule
an isotope and a molecule; an isotope
a compound and an isotope; a molecule
a molecule and a compound; a compound
a molecule and a compound; a molecule 68

69. What do elements with atomic numbers 6, 14, and 22 have in common?
same number of electrons
same atomic mass
same number of valence electrons and will form the same number of covalent bonds
all of the above
none of the above
Answer: C
This question highlights the fact that these elements have the same basic structures and therefore the same basic properties.
*added “number of…electrons” to option C 69

70. What do elements with atomic numbers 6, 14, and 22 have in common?
same number of electrons
same atomic mass
same number of valence electrons and will form the same number of covalent bonds
all of the above
none of the above
*added “number of….electrons” to option C 70

71. What type of bond is very prevalent in lipids and gives lipids their properties?
polar covalent
nonpolar covalent
strong ionic
weak ionic
hydrogen
Answer: B
The nonpolar covalent bond is very common in C—C and C—H bonds. 71

72. What type of bond is very prevalent in lipids and gives lipids their properties?
polar covalent
nonpolar covalent
strong ionic
weak ionic
hydrogen 72

73. An atom of oxygen has an atomic number of 8
An atom of oxygen has an atomic number of 8. How many electrons are in the first, second, and third electron shells, respectively?
2, 3, 3
2, 6, 0
8, 0, 0
0, 4, 4
none of the above
Answer: B 73

74. An atom of oxygen has an atomic number of 8
An atom of oxygen has an atomic number of 8. How many electrons are in the first, second, and third electron shells, respectively?
2, 3, 3
2, 6, 0
8, 0, 0
0, 4, 4
none of the above 74

75. What numbers must be placed as coefficients in the blanks for the chemical reaction below in order to ensure that matter is conserved?
1; 1; 1
4; 3; 4
2; 1; 2
3; 4; 3
0; 3; 4
Fe3O4  __C  __Fe  __CO
Answer: B 75

76. What numbers must be placed as coefficients in the blanks for the chemical reaction below in order to ensure that matter is conserved?
1; 1; 1
4; 3; 4
2; 1; 2
3; 4; 3
0; 3; 4
Fe3O4  __C  __Fe  __CO 76

77. Of the four most commonly found elements in the human body, which has the most valence electrons?
Answer: A 77

78. Of the four most commonly found elements in the human body, which has the most valence electrons?78

79. Lithium and fluorine are most likely to form which type of bond?
polar covalent
nonpolar covalent
ionic
hydrogen
A and B are equally likely
Answer: C 79

80. Lithium and fluorine are most likely to form which type of bond?
polar covalent
nonpolar covalent
ionic
hydrogen
A and B are equally likely 80

81. Carbon-14 dating works for fossils up to about 75,000 years old
Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14C be used to date dinosaur bones?
Yes; the bones continued to take in 14C, even after the dinosaur died.
No; the 14C present in the dinosaur when it died would decay too much to be measured after 65.5 million years.
No; 14C can only be used to date dinosaur teeth, which are much stronger than bones.
Yes; the bones contained 14C when the dinosaur died so it can be measured to determine the fossil’s age.
Answer: B
After 65.5 million years, too much of the 14C would have decayed to be able to measure it. 81

82. Carbon-14 dating works for fossils up to about 75,000 years old
Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14C be used to date dinosaur bones?
Yes; the bones continued to take in 14C, even after the dinosaur died.
No; the 14C present in the dinosaur when it died would decay too much to be measured after 65.5 million years.
No; 14C can only be used to date dinosaur teeth, which are much stronger than bones.
Yes; the bones contained 14C when the dinosaur died so it can be measured to determine the fossil’s age. 82

83. Radioactive uranium-235 has a half-life of 704 million years
Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils?
Yes; after 65.5 million years only about one-tenth of the 235U would have decayed, leaving plenty to measure in the fossils.
No; the dinosaurs went extinct too recently to use a radioisotope with a half-life of 704 million years.
No; only about one tenth of the 235U would have decayed after 65.5 million years, not leaving enough to measure in the fossils.
Yes; but only for dinosaurs that lived more than 704 million years ago.
Answer: A 83

84. Radioactive uranium-235 has a half-life of 704 million years
Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils?
Yes; after 65.5 million years only about one-tenth of the 235U would have decayed, leaving plenty to measure in the fossils.
No; the dinosaurs went extinct too recently to use a radioisotope with a half-life of 704 million years.
No; only about one tenth of the 235U would have decayed after 65.5 million years, not leaving enough to measure in the fossils.
Yes; but only for dinosaurs that lived more than 704 million years ago. 84