1. The Structure of Matter
Preview
Understanding Concepts
Reading Skills
Interpreting Graphics

2. Understanding Concepts
1. What causes atoms to form chemical bonds with other atoms?
A. Atoms are more stable when they give away electrons.
B. When two atoms get close together, they merge into one.
C. The interaction of valence electrons forms a more stable configuration.
D. The attraction of the nuclei for one another causes atoms to share electrons.

3. Understanding Concepts, continued
1. What causes atoms to form chemical bonds with other atoms?
A. Atoms are more stable when they give away electrons.
B. When two atoms get close together, they merge into one.
C. The interaction of valence electrons forms a more stable configuration.
D. The attraction of the nuclei for one another causes atoms to share electrons.

4. Understanding Concepts, continued
2. How many atoms of oxygen are in one formula unit of aluminum sulfate, Al2(SO4)3?
F. 3
G. 4
H. 8
I. 12

5. Understanding Concepts, continued
2. How many atoms of oxygen are in one formula unit of aluminum sulfate, Al2(SO4)3?
F. 3
G. 4
H. 8
I. 12

6. Understanding Concepts, continued
3. A nitride anion, N3–, has a charge of 3–. What is the charge of a titanium cation in the compound Ti3N2?
A. 2+
B. 2–
C. 3+
D. 3–

7. Understanding Concepts, continued
3. A nitride anion, N3–, has a charge of 3–. What is the charge of a titanium cation in the compound Ti3N2?
A. 2+
B. 2–
C. 3+
D. 3–

8. Understanding Concepts, continued
4. What is the condensed structural formula for the n-alkane heptane, which has a molecular formula of C7H16?
F. C7H16
G. (CH2)6CH4
H. C3H4(CH3)4
I. CH3(CH2)5CH3

9. Understanding Concepts, continued
4. What is the condensed structural formula for the n-alkane heptane, which has a molecular formula of C7H16?
F. C7H16
G. (CH2)6CH4
H. C3H4(CH3)4
I. CH3(CH2)5CH3

10. Understanding Concepts, continued
5. The difference between the three types of chemical bonds—covalent, ionic, and metallic—is what happens to valence electrons that are part of the bond. Compare the three types of bonds based on valence electrons.

11. Understanding Concepts, continued
5. The difference between the three types of chemical bonds—covalent, ionic, and metallic—is what happens to valence electrons that are part of the bond. Compare the three types of bonds based on valence electrons.
Answer: In a covalent bond, the valence electrons are shared by two atoms. In an ionic bond, an electron is transferred from one atom to another. In a metallic bond, electrons move freely from one atom to another.

12. Reading Skills SPIDER SILK
Spider silk is one of the strongest known fibers. It is strong enough to support the spider and has enough elasticity to absorb the energy of the collision of a flying insect. The strength comes from the covalent bonds between units of the amino acid polymer of which spider silk, a protein, is made. The elasticity is the result of interactions between different parts of the molecule. Coils or folds in the protein expand on impact.
Spiders can make at least seven kinds of silk for different purposes by varying the amino acids that make up the silk. Scientists studying the structure of silk have identified some of the structures that account for silk’s properties. They have even found ways to mimic the properties of spider silk in synthetic fibers. However, there is still much for scientists to learn from the amazing natural properties of spider silk.

13. Reading Skills, continued
6. How do the various kinds of spider silk differ based on their protein structures?

14. Reading Skills, continued
6. How do the various kinds of spider silk differ based on their protein structures?
Answer: Different kinds of spider silk have different amino acids, which gives them different properties.

15. Reading Skills, continued
7. Which of the following describes the properties of spider silk?
A. heavy and strong
B. light and flimsy
C. strong and elastic
D. rigid and heavy

16. Reading Skills, continued
7. Which of the following describes the properties of spider silk?
A. heavy and strong
B. light and flimsy
C. strong and elastic
D. rigid and heavy

17. Reading Skills, continued
8. Which of the following best describes what scientists have learned about spider silk?
F. All of its properties have been explained.
G. Scientists have made synthetic fibers with properties similar to spider silk.
H. All spider silk has the same chemical structure.
I. The unique properties of spider silk remain a mystery.

18. Reading Skills, continued
8. Which of the following best describes what scientists have learned about spider silk?
F. All of its properties have been explained.
G. Scientists have made synthetic fibers with properties similar to spider silk.
H. All spider silk has the same chemical structure.
I. The unique properties of spider silk remain a mystery.

19. Interpreting Graphics
The illustration below models how water molecules are arranged in the liquid state. Use this illustration to answer question 9.
9. Compare the forces of attraction between the atoms of a water molecule to the forces of attraction between two water molecules.

20. Interpreting Graphics, continued
9. Compare the forces of attraction between the atoms of a water molecule to the forces of attraction between two water molecules.
Answer: The forces of attraction between the oxygen and hydrogen atoms of the molecule are very strong. The forces between atoms on different molecules are weak.

21. Interpreting Graphics, continued
The following graphic shows a model of one molecular unit of the amino acid alanine, which has a structural formula of
CH3CHNH2COOH. Use this graphic to answer questions 10–11.

22. Interpreting Graphics, continued
10. What letter represents carbon in the model?
A. A
B. B
C. C
D. D

23. Interpreting Graphics, continued
10. What letter represents carbon in the model?
A. A
B. B
C. C
D. D

24. Interpreting Graphics, continued
11. Atoms of which two elements share a double covalent bond in alanine?

25. Interpreting Graphics, continued
11. Atoms of which two elements share a double covalent bond in alanine?
Answer: C and A