1. Chapter 2: Small Molecules: Structure and Behavior CHAPTER 2 Small Molecules: Structure and Behavior

2. Chapter 2: Small Molecules: Structure and Behavior Atoms: The Constituents of Matter Atoms: The Constituents of Matter Chemical Bonds: Linking Atoms Together Chemical Bonds: Linking Atoms Together Chemical Reactions: Atoms Change Partners Chemical Reactions: Atoms Change Partners Water: Structure and Properties Water: Structure and Properties

3. Chapter 2: Small Molecules: Structure and Behavior Acids, Bases, and the pH Scale Acids, Bases, and the pH Scale The Properties of Molecules The Properties of Molecules

4. Chapter 2: Small Molecules: Structure and Behavior Atoms: The Constituents of Matter Matter is composed of atoms with positively charged nuclei of protons and neutrons surrounded by negatively charged electrons.Matter is composed of atoms with positively charged nuclei of protons and neutrons surrounded by negatively charged electrons.4

5. Chapter 2: Small Molecules: Structure and Behavior Atoms: The Constituents of Matter Of the many elements in nature, only a few make up the bulk of living systems.Of the many elements in nature, only a few make up the bulk of living systems. Review Figure 2.1 2.1 5

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7. Chapter 2: Small Molecules: Structure and Behavior Atoms: The Constituents of Matter Isotopes of an element differ in numbers of neutrons. Some are radioactive.Isotopes of an element differ in numbers of neutrons. Some are radioactive. Review Figure 2.2 2.2 7

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9. Chapter 2: Small Molecules: Structure and Behavior Atoms: The Constituents of Matter Electrons are distributed in shells of orbitals containing a maximum of two.Electrons are distributed in shells of orbitals containing a maximum of two. Review Figures 2.4, 2.5 2.42.52.42.59

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12. Chapter 2: Small Molecules: Structure and Behavior Atoms: The Constituents of Matter An atom can combine with other atoms to form molecules. Review Table 2.1An atom can combine with other atoms to form molecules. Review Table 2.12.1 12

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14. Chapter 2: Small Molecules: Structure and Behavior Chemical Bonds: Linking Atoms Together Covalent bonds form when two atomic nuclei share one or more pairs of electrons.Covalent bonds form when two atomic nuclei share one or more pairs of electrons. They have spatial orientations that give molecules three-dimensional shapes.They have spatial orientations that give molecules three-dimensional shapes. Review Figures 2.6, 2.7, Table 2.2 2.62.72.22.62.72.214

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17. Chapter 2: Small Molecules: Structure and Behavior Table 2.2 table 02-02.jpg

18. Chapter 2: Small Molecules: Structure and Behavior Chemical Bonds: Linking Atoms Together Nonpolar covalent bonds form when the electronegativities of two atoms are approximately equal.Nonpolar covalent bonds form when the electronegativities of two atoms are approximately equal. When atoms with strong electronegativity (such as oxygen) bond to atoms with weaker electronegativity (such as hydrogen), a polar covalent bond forms, in which one end is  + and the other is  –.When atoms with strong electronegativity (such as oxygen) bond to atoms with weaker electronegativity (such as hydrogen), a polar covalent bond forms, in which one end is  + and the other is  –. Review Figure 2.8, Table 2.3 2.82.32.82.318

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20. Chapter 2: Small Molecules: Structure and Behavior Table 2.3 table 02-03.jpg

21. Chapter 2: Small Molecules: Structure and Behavior Chemical Bonds: Linking Atoms Together Hydrogen bonds form between a  + hydrogen atom in one molecule and a  – nitrogen or oxygen atom in another molecule.Hydrogen bonds form between a  + hydrogen atom in one molecule and a  – nitrogen or oxygen atom in another molecule. Review Figure 2.9 2.9 21

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23. Chapter 2: Small Molecules: Structure and Behavior Chemical Bonds: Linking Atoms Together Ions, electrically charged bodies, form when an atom gains or loses one or more electrons.Ions, electrically charged bodies, form when an atom gains or loses one or more electrons. Ionic bonds are electrical attractions between oppositely charged ions.Ionic bonds are electrical attractions between oppositely charged ions. Review Figures 2.10, 2.11 2.102.112.102.1123

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26. Chapter 2: Small Molecules: Structure and Behavior Chemical Bonds: Linking Atoms Together Nonpolar molecules do not interact directly with polar substances. They are attracted to each other by very weak bonds called van der Waals forces. Review Figure 2.122.12 26

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28. Chapter 2: Small Molecules: Structure and Behavior Chemical Reactions: Atoms Change Partners In chemical reactions, substances change their atomic compositions and properties.In chemical reactions, substances change their atomic compositions and properties. Energy is either released or added.Energy is either released or added. Matter and energy are not created or destroyed, but change form.Matter and energy are not created or destroyed, but change form.28

29. Chapter 2: Small Molecules: Structure and Behavior Chemical Reactions: Atoms Change Partners Combustion reactions are oxidation- reduction reactions.Combustion reactions are oxidation- reduction reactions. Fuel is converted to carbon dioxide and water, while energy is released as heat and light.Fuel is converted to carbon dioxide and water, while energy is released as heat and light. In living cells, these reactions occur in multiple steps.In living cells, these reactions occur in multiple steps. Review Figure 2.13 2.13 29

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31. Chapter 2: Small Molecules: Structure and Behavior Water: Structure and Properties Water’s molecular structure and capacity to form hydrogen bonds give it unusual properties significant for life.Water’s molecular structure and capacity to form hydrogen bonds give it unusual properties significant for life. Review Figure 2.15 2.15 31

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33. Chapter 2: Small Molecules: Structure and Behavior Water: Structure and Properties Cohesion of water molecules results in a high surface tension.Cohesion of water molecules results in a high surface tension. Water’s high heat of vaporization assures cooling when it evaporates.Water’s high heat of vaporization assures cooling when it evaporates.33

34. Chapter 2: Small Molecules: Structure and Behavior Water: Structure and Properties Solutions are substances dissolved in water.Solutions are substances dissolved in water. Concentration is the amount of a given substance in a given amount of solution.Concentration is the amount of a given substance in a given amount of solution. Most biological substances are dissolved at very low concentrations.Most biological substances are dissolved at very low concentrations.34

35. Chapter 2: Small Molecules: Structure and Behavior Acids, Bases, and the pH Scale Acids are substances that donate hydrogen ions.Acids are substances that donate hydrogen ions. Bases are those that accept hydrogen ions.Bases are those that accept hydrogen ions.35

36. Chapter 2: Small Molecules: Structure and Behavior Acids, Bases, and the pH Scale The pH of a solution is the negative logarithm of the hydrogen ion concentration. Values lower than pH 7 indicate an acidic solution. Values above pH 7 indicate a basic solution. Review Figure 2.182.1836

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38. Chapter 2: Small Molecules: Structure and Behavior Acids, Bases, and the pH Scale Buffers are systems of weak acids and bases that limit the change in pH when hydrogen ions are added or removed.Buffers are systems of weak acids and bases that limit the change in pH when hydrogen ions are added or removed. Review Figure 2.19 2.19 38

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40. Chapter 2: Small Molecules: Structure and Behavior The Properties of Molecules Molecules vary in size, shape, reactivity, solubility, and other chemical properties.Molecules vary in size, shape, reactivity, solubility, and other chemical properties.40

41. Chapter 2: Small Molecules: Structure and Behavior The Properties of Molecules Functional groups make up part of a larger molecule and have particular chemical properties. 41

42. Chapter 2: Small Molecules: Structure and Behavior The Properties of Molecules The consistent chemical behavior of functional groups helps us understand the properties of the molecules that contain them. Review Figure 2.202.20 42

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45. Chapter 2: Small Molecules: Structure and Behavior The Properties of Molecules Structural and optical isomers have the same kinds and numbers of atoms, but differ in their structures and properties.Structural and optical isomers have the same kinds and numbers of atoms, but differ in their structures and properties. Review Figure 2.21 2.21 45

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