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

Chapter 2: Small Molecules: Structure and Behavior

CHAPTER 2Small Molecules:

Structure and Behavior


Chapter 2: Small Molecules: Structure and BehaviorAtoms: The Constituents of MatterAtoms: The Constituents of Matter

Chemical Bonds: Linking Atoms TogetherChemical Bonds: Linking Atoms Together

Chemical Reactions: Atoms Change Chemical Reactions: Atoms Change PartnersPartners

Water: Structure and PropertiesWater: Structure and Properties


Chapter 2: Small Molecules: Structure and BehaviorAcids, Bases, and the pH ScaleAcids, Bases, and the pH Scale

The Properties of MoleculesThe Properties of Molecules


Atoms: The Constituents of Matter

• Matter is composed of atoms with Matter is composed of atoms with positively charged nuclei of protons positively charged nuclei of protons and neutrons surrounded by and neutrons surrounded by negatively charged electrons. negatively charged electrons.

44



• Of the many elements in nature, only a Of the many elements in nature, only a few make up the bulk of living few make up the bulk of living systems. systems.

Review Figure Review Figure 2.12.1

55


2.1

Figure 2.1Figure 2.1

figure 02-01.jpg



• Isotopes of an element differ in Isotopes of an element differ in numbers of neutrons. Some are numbers of neutrons. Some are radioactive. radioactive.

Review Figure Review Figure 2.22.2

77


2.2


figure 02-02.jpg



• Electrons are distributed in shells of Electrons are distributed in shells of orbitals containing a maximum of two. orbitals containing a maximum of two.

Review Figures Review Figures 2.42.4, , 2.52.5

99


2.4


figure 02-04.jpg


2.5


figure 02-05.jpg


Atoms: The Constituents of Matter• An atom can combine with other An atom can combine with other

atoms to form molecules. Review atoms to form molecules. Review Table Table 2.12.1

1212


Table 2.1

Table 2.1Table 2.1

table 02-01.jpg


Chemical Bonds: Linking Atoms Together

• Covalent bonds form when two atomic Covalent bonds form when two atomic nuclei share one or more pairs of nuclei share one or more pairs of electrons. electrons.

• They have spatial orientations that They have spatial orientations that give molecules three-dimensional give molecules three-dimensional shapes. shapes.

Review Figures 2.6, 2.7, Table 2.2Review Figures 2.6, 2.7, Table 2.2

1414


2.6


figure 02-06.jpg


2.7


figure 02-07.jpg


Table 2.2

Table 2.2Table 2.2

table 02-02.jpg


Chemical Bonds: Linking Atoms Together• Nonpolar covalent bonds form when Nonpolar covalent bonds form when

the electronegativities of two atoms the electronegativities of two atoms are approximately equal. are approximately equal.

• When atoms with strong When atoms with strong electronegativity (such as oxygen) electronegativity (such as oxygen) bond to atoms with weaker bond to atoms with weaker electronegativity (such as hydrogen), a electronegativity (such as hydrogen), a polar covalent bond forms, in which polar covalent bond forms, in which one end is one end is ++ and the other is and the other is ––. .

Review Figure Review Figure 2.82.8, Table 2.3, Table 2.3

1818


2.8


figure 02-08.jpg


Table 2.3

Table 2.3Table 2.3

table 02-03.jpg



• Hydrogen bonds form between a Hydrogen bonds form between a ++ hydrogen atom in one molecule and a hydrogen atom in one molecule and a –– nitrogen or oxygen atom in another nitrogen or oxygen atom in another molecule. molecule.

Review Figure 2.9Review Figure 2.9

2121


2.9


figure 02-09.jpg



• Ions, electrically charged bodies, form Ions, electrically charged bodies, form when an atom gains or loses one or when an atom gains or loses one or more electrons. more electrons.

• Ionic bonds are electrical attractions Ionic bonds are electrical attractions between oppositely charged ions. between oppositely charged ions.

Review Figures 2.10, 2.11 Review Figures 2.10, 2.11

2323


2.10


figure 02-10.jpg


2.11


figure 02-11.jpg



• 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 2.1226


2.12


figure 02-12.jpg


Chemical Reactions: Atoms Change Partners

• In chemical reactions, substances In chemical reactions, substances change their atomic compositions and change their atomic compositions and properties. properties.

• Energy is either released or added. Energy is either released or added.

• Matter and energy are not created or Matter and energy are not created or destroyed, but change form. destroyed, but change form.

2828


Chemical Reactions: Atoms Change Partners

• Combustion reactions are oxidation-Combustion reactions are oxidation-reduction reactions. reduction reactions.

• Fuel is converted to carbon dioxide Fuel is converted to carbon dioxide and water, while energy is released as and water, while energy is released as heat and light. heat and light.

• In living cells, these reactions occur in In living cells, these reactions occur in multiple steps. multiple steps.



2.13


figure 02-13.jpg


Water: Structure and Properties

• Water’s molecular structure and Water’s molecular structure and capacity to form hydrogen bonds give capacity to form hydrogen bonds give it unusual properties significant for life. it unusual properties significant for life.


3131


2.15


figure 02-15.jpg



• Cohesion of water molecules results in Cohesion of water molecules results in a high surface tension. a high surface tension.

• Water’s high heat of vaporization Water’s high heat of vaporization assures cooling when it evaporates. assures cooling when it evaporates.

3333



• Solutions are substances dissolved in Solutions are substances dissolved in water.water.

• Concentration is the amount of a given Concentration is the amount of a given substance in a given amount of substance in a given amount of solution. solution.

• Most biological substances are Most biological substances are dissolved at very low concentrations. dissolved at very low concentrations.

3434


Acids, Bases, and the pH Scale

• Acids are substances that donate Acids are substances that donate hydrogen ions. hydrogen ions.

• Bases are those that accept hydrogen Bases are those that accept hydrogen ions. ions.

3535



• 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 2.18

3636


2.18


figure 02-18.jpg



• Buffers are systems of weak acids and Buffers are systems of weak acids and bases that limit the change in pH when bases that limit the change in pH when hydrogen ions are added or removed. hydrogen ions are added or removed.


3838


2.19


figure 02-19.jpg


The Properties of Molecules• Molecules vary in size, shape, Molecules vary in size, shape,

reactivity, solubility, and other reactivity, solubility, and other chemical properties. chemical properties.

4040


The Properties of Molecules• Functional groups make up part of a

larger molecule and have particular chemical properties.

41


The Properties of Molecules• The consistent chemical behavior of

functional groups helps us understand the properties of the molecules that contain them.

Review Figure 2.2042


2.20 – Part 1

Figure 2.20 – Part 1Figure 2.20 – Part 1

figure 02-20a.jpg


2.20 – Part 2

Figure 2.20 – Part 2Figure 2.20 – Part 2

figure 02-20b.jpg


The Properties of Molecules• Structural and optical isomers have Structural and optical isomers have

the same kinds and numbers of atoms, the same kinds and numbers of atoms, but differ in their structures and but differ in their structures and properties. properties.


4545


2.21


figure 02-21.jpg

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

Documents

Transcript of Chapter 2: Small Molecules: Structure and Behavior CHAPTER 2 Small Molecules: Structure and...