Copyright © 2005 Pearson Prentice Hall, Inc. Chapter 2 Atoms, Molecules, and Life

Copyright © 2005 Pearson Prentice Hall, Inc.

Chapter 2

• Atoms, Molecules, and Life


2.1 What Are Atoms?

• 2.1.1 Atoms, the Basic Structural Units of Matter, Are Composed of Still Smaller Particles– Figure 2.1 Atomic models (p. 22) – Table 2.1 Common Elements Important in

Living Organisms (p. 22) – Figure E2.1 How positron emission

tomography works (p.23)

Helium (He)

nn

Hydrogen (H)

electronshell

nucleus

e-

p+ p+

p+

e-

e-

Hydrogen (H)

electronshell

nucleus

e-

p+

Helium (He)

nn

e-

p+

p+

e-


2.1 What Are Atoms?

– 2.1.1.1 Electrons Orbit the Nucleus at Fixed Distances, Forming Electron Shells That Correspond to Different Energy Levels

• Figure 2.2 Electron shells in atoms (p. 24)

Carbon (C) Oxygen (O) Phosphorus (P) Calcium (Ca)CaOC P

4e– 6e–

5e–

2e–

8e–

8e–

8e–

2e– 2e–

2e–

2e–

6p+ 8p+ 15p+ 20p+6n 8n 16n 20n


2.2 How Do Atoms Interact to Form Molecules?

• 2.2.1 Atoms Interact with Other Atoms When There Are Vacancies in Their Outermost Electron Shells

• 2.2.2 Charged Atoms Called Ions Interact to Form Ionic Bonds– Figure 2.3 (Hide/Reveal) The formation of

ions and ionic bonds (p. 25)

Sodium atom (neutral)

Na

17p+11p+11n

11p+

11n

Chlorine atom (neutral)

18n

17p+

18n

Cl

Sodium ion (+) Chloride ion (–)

Cl–

Cl–

Na+

Na+

An ionic compound: NaCl

Sodium atom (neutral)

Na

17p+11p+11n

Chlorine atom (neutral)

18n

Cl

11p+11n

17p+18n

Sodium ion (+) Chloride ion (–)

Cl–Na+

Cl–

Na+

An ionic compound: NaCl



• 2.2.3 Uncharged Atoms Can Become Stable by Sharing Electrons, Forming Covalent Bonds– Figure 2.4 Covalent bonds involve shared

electrons (p. 26) – Table 2.2 Chemical Bonds (p. 26)

Nonpolar covalent bonding Polar covalent bonding

Water (H–O–H or H2O)

Hydrogen (H–H or H2)

Oxygen (O=O or O2)

(slightly negative)

(slightly positive)

8p+8n

8p+8n

8p+8n



– 2.2.3.1 Most Biological Molecules Utilize Covalent Bonding

• Unnumbered Figure 3 Bonding Patterns of Atoms Commonly Found in Biological Molecules (p. 27)

• Table 2.3 Bonding Patterns of Atoms Commonly Found in Biological Molecules (p. 27)



– 2.2.3.2 Electron Sharing Determines Whether a Covalent Bond Is Nonpolar or Polar

– 2.2.3.3 Free Radicals Are Highly Reactive and Can Damage Cells

• 2.2.4 Hydrogen Bonds Are Weaker Electrical Attractions Between or Within Molecules with Polar Covalent Bonds– Figure 2.5 Hydrogen bonds (p. 28)

O(–)

H(+)

hydrogrenbonds

H(+)

H(+)

H(+)

O(–)


2.3 Why Is Water So Important to Life?

• 2.3.1 Water Interacts with Many Other Molecules– Figure 2.6 Water as a solvent (p. 29) – Figure 2.7 Water dissolves many biological

molecules (p. 29)

Cl–

Cl–

Na+

Na+

Na+

H

H

H

H

O

O–

hydrogen bond

hydroxylgroup

glucose

water



• 2.3.2 Water Molecules Tend to Stick Together– Figure 2.8 Cohesion among water

molecules (p. 30) – Unnumbered Figure 1 Ionization of Water

(p. 30)

O O

hydrogen ion(H+)

hydroxide ion(OH–)

water(H2O)

+(+)

(–)

H H H

H



• 2.3.3 Water-Based Solutions Can Be Acidic, Basic, or Neutral– Figure 2.9 The pH scale (p. 31) – Unnumbered Figure 2 Comparison of liquid

and solid phases of water (p. 32)

1-molar hydrochloricacid (HCI)

stomach acidlime juice

lemon juice

"acid rain" (2.5–5.5)vinegar, cola, orange juice,tomatoes

beer

black coffee, tea

normal rain (5.6)urine (5.7)

pure water (7.0)salivablood, sweat (7.4)

seawater (7.8–8.3)

baking soda

phosphate detergentschlorine bleachmilk of magnesia

household ammoniasome detergents(without phosphates)

washing soda

oven cleaner

1-molar sodiumhydroxide (NaOH)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

pHvalueH+ concentration

(moles/liter)100

10–1

10–2

10–3

10–4

10–5

10–6

10–7

–6

–7

–8

–9

–10

–11

–12

–13

–14

10–8

10–9

10–10

10–11

10–12

10–13

10–14

neutral

(H+ = OH–)

incr

easi

ngly

aci

dic

(H+ >

OH

– )in

cre

asi

ng

ly b

asi

c (

H+ <

OH

– )

1-molar hydrochloricacid (HCI)

stomach acidlime juice

lemon juice

"acid rain" (2.5–5.5)vinegar, cola, orange juice,tomatoes

beer

black coffee, tea

normal rain (5.6)urine (5.7)

0

1

2

3

4

5

6

pHvalue

H+ concentration(moles/liter)

100

10–1

10–2

10–3

10–1

10–5

10–6

incr

easi

ngly

aci

dic

(H

+ >

OH

– )

incr

easi

ngly

bas

ic (

H+ <

OH

–)

pure water (7.0)alivablood, sweat (7.4)

seawater (7.8–8.3)

baking soda

phosphate detergentschlorine bleachmilk of magnesia

household ammoniasome detergents(without phosphates)

washing soda

oven cleaner

1-molar sodiumhydroxide (NaOH)

7

8

9

10

11

12

13

14

10–7

10–8

10–9

10–10

10–11

10–12

10–13

10–14

neutral(H+ = OH–)



– 2.3.3.1 A Buffer Helps Maintain a Solution at a Relatively Constant pH

• 2.3.4 Water Moderates the Effects of Temperature Changes

• 2.3.5 Water Forms an Unusual Solid: Ice– Figure E2.2 Chocolate (p. 33)

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Copyright © 2005 Pearson Prentice Hall, Inc. Chapter 2 Atoms, Molecules, and Life