The Chemical Elements

Chapter 11

The Chemical Elements

Chapter 11 begins the four-chapter chemistry section by discussing the chemical classification of matter, the discovery and occurrences of the elements, the periodic table, and the basics of compound nomenclature. Two A chapter Highlights discusses the Lake Nyos tragedy and the work of Mendeleev.

Much of the material discussed in this chapter is necessary for dealing successfully with the next three chapters. The student already should have learned the names and symbols of the 45 46 elements in Table 10.2 of the textbook and will now need to learn the names and formulas of the eight polyatomic ions listed in Table 11.6 and the ten common compounds shown in Table 11.3. Probably the most efficient and effective way of doing this is to make and use flashcards. For simplicity, our discussion of chemistry will involve primarily the representative (A Group) elements.

The student will need to refer frequently to the periodic table on the inside front cover of the textbook. We recommend that a wall chart of the periodic table be on display in the lecture classroom at all times, including during exams. The material in this chapter is so fundamental that we recommend that it be covered in its entirety.

DEMONSTRATIONS

When discussing the differences between compounds and mixtures, it is useful to pass around two Erlenmeyer flasks, one containing the compound zinc sulfide and the other containing a heterogeneous mixture of powdered sulfur and mossy zinc. For additional ideas on demonstrations, refer to the publications listed in the Teaching Aids section.

A historical periodic poster that pictures the elements and gives some of their histories helps the students to visualize many of the descriptions given in the textbook. It can be obtained from places such as Fisher EMD (S45527-1) for about $25 and might be posted on the bulletin board in the classroom. Perhaps the best basic chemistry film ever made is The Periodic Table, available from Media Guild. For additional ideas on appropriate audiovisual material, refer to the catalogs of the audiovisual suppliers listed in the Teaching Aids section.

ANSWERS TO MATCHING QUESTIONS

a. 415 b. 1117 c. 2216 d. 2624 e. 8 21 f. 13 1 g. 25 10 h. 2 13 i. 21 2 j. 16 3 k. 7 26 l. 18 28 m. 1
m. 27 n. 6 25 o. 15 4 p. 10 7 q. 23 9 r. 12 11 s. 5 19 t. 17 18 u. 9 8 v. 24 5 w. 14 22 x. 20 14 y. 3 z. 19
y. 12 z. 6 aa. 20 bb. 23

ANSWERS TO MULTIPLE-CHOICE QUESTIONS

1. c 2. b a 3. d b 4. b d 5. b 6. c d 7. a c 8. d b 9. b d 10. c a 11. d a 12. c

ANSWERS TO FILL-IN-THE-BLANK QUESTIONS

1. physical organic 2. experiment heterogeneous 3. COscientific method 42. sight 4. hydrogen 5. limitations molecules 6. standard unitbromine
7. allotropes longer 8. Mendeleev fundamental 9. time or second four 10. 103 or 1000 decreases 11. liter nitrate 12. massnoble gases

ANSWERS TO VISUAL CONNECTION

ANSWERS TO REVIEW SHORT-ANSWER QUESTIONS

1.. Chemistry deals with the composition and structure of matter and the reactions by which substances are changed into other substances.

2.. Physical, analytical, organic, inorganic, and biochemistry.Physical chemistry applies the theories of physics (especially thermodynamics) to the study of chemical reactions.

Analytical chemistry deals with the identification of substances present in a material and how much of each substance is present.

Organic chemistry is the study of compounds that contain carbon. Inorganic chemistry is the study of compounds that do not contain carbon. Biochemistry studies the chemical reactions that occur in living organisms. 2. c

Inorganic chemistry is the study of compounds that do not contain carbon. Biochemistry studies the chemical reactions that occur in living organisms. 2. c

33. c

4. b

5.b

6.. Illustrations b and d show different atoms and/or molecules and thus represent mixtures. Illustration e shows identical molecules composed of the same two elements and so represents a compound. Illustrations a and c show identical atoms and identical diatomic molecules of atoms of the same element, respectively, and thus represent elements. Illustration c shows diatomic molecules of an element, whereas e shows diatomic molecules of a compound.

74.. A pure substance is a type of matter in which all samples have fixed composition and identical properties, whereas a mixture is a type of matter composed of varying proportions of two or more substances that are just physically mixed, not chemically combined. Thus samples of a mixture can have variable composition and properties.

5. Mixtures can be separated into, and prepared from, pure substances by physical processes.

6. An element is a pure substance in which all the atoms have the same number of protons; elements cannot be further broken down by chemical processes. A compound is a substance composed of two or more elements chemically combined in a definite, fixed proportion by mass.An element is a pure substance in which all the atoms have the same number of protons; elements cannot be further broken down by chemical processes. A compound is a substance composed of two or more elements chemically combined in a definite, fixed proportion by mass.

78.. Mixtures can be separated into, and prepared from, pure substances by physical processes. Compounds can be prepared from, and decomposed into, elements by chemical processes only.

98.. An appropriate set of examples would be: bronze, salt water, air.

109. Water is the solvent, and sugar is the solute. When no more sugar dissolves, the solution is saturated.

11.Carbon dioxide. The carbon dioxide escapes from the solution in an open container due to an increase in temperature and a decrease in pressure.

12. a

13. d

14. b

1510. Twelve. Any six of the following can be named: gold, silver, lead, copper, tin, iron, carbon, sulfur, antimony, arsenic, mercury, bismuth.

1611.. Humphry Davy set a record for the discovery of elements (six) with the new invention called the battery.

1712.. At present, 114 about 115 elements are known for sure, 88 of which occur naturally on Earth.

18. a

19. b

2013.. (a)) Oxygen and silicon.

(b)) Iron and nickel.

(c)) Oxygen and carbon.

(d)) Nitrogen and oxygen.

(e)) Hydrogen and helium.

2114.. 03O3

22. d

23. c

24. d

2515. Dmitri Mendeleev developed the periodic table in 1869.

2616.. Atomic number is now used. The periodic trends in the table are based on atomic number, which correlates more exactly with electron configuration than does atomic mass.

2717.. The properties of elements are periodic functions of their atomic numbers., which means that the elements' properties show regular trends, with similar properties recurring at regular intervals.

2818. (a) Periods.

(b) Groups.

2919.. The valence electrons are the ones that form chemical bonds.

3020.. (a)) Metals usually have 1 to 3 valence electrons; nonmetals usually have 4 to 8.

(b)) Metals are good conductors of heat and electricity; nonmetals are not.

(c)) Metals are solid at room temperature (except for Hg); many nonmetals are gaseous or liquid.

3121.. Metallic character (a) decreases from left to right across a period, and (b) increases down a group. Cesium is the most metallic element, and fluorine is the most nonmetallic.

3222.. Semimetals or metalloids, located next to the staircase line in the periodic table.

3323. Mercury and bromine are liquid. Hydrogen, oxygen, nitrogen, fluorine, and chlorine, (plus six noble gases) are gases.

3424.. Atomic size (a) decreases from left to right across a period, and (b) increases down a group.

35. d

36. a

3725.. The ammonium ion.

3826.. (a)) An atom is the smallest particle of an element; a molecule is an electrically neutral particle composed of two or more atoms chemically bound together.

(b)) An atom is electrically neutral; an ion has an electrical charge.

(c)) A molecule is an electrically neutral particle composed of two or more atoms; a polyatomic ion is an electrically charged particle composed of two or more atoms.

3927. Because the nomenclature rule for metal-nonmetal compounds is different from the rule for nonmetal-nonmetal compounds.

40. c

41. d

4228. Because they have the same number of valence electrons.

4329.. The noble gases are chemically unreactive. They have low boiling and melting points.

4430.. Fluorine and chlorine are gases, bromine is liquid, and iodine is solid. Fluorine is the most reactive element.

4531.. Sodium iodide is added to prevent thyroid problems due to iodine deficiency.

4632.. NaHC03 NaHCO3 is baking soda.

4733.. (a)) Calcium phosphate.

(b)) Calcium carbonate.

4834.. The Hindenburg syndrome is the term applied to the reluctance to use hydrogen as a fuel.

ANSWERS TO APPLYING- YOUR- KNOWLEDGE QUESTIONS

1.. It should resemble thallium (Tl), because counting across in the periodic table shows that it would be in the same group as thallium (Tl).

2.. Although homogenized milk looks uniform to the unaided eye, a microscope shows fat globules dispersed throughout the water. Therefore, it is not a true solution, because it is not mixed on the atomic or molecular level.

3.. Graphite makes a good lubricant because of its slipperiness, so the key should turn easily.

4.. Being “snobs” refers to the noble gases’ lack of chemical reactivity, or “interaction,” with other elements.

5.. Fluorine is the most reactive element of all and thus is so dangerous that it should be handled only by experts.

6.. The event would likely be described in superstitious or supernatural terms.was likely due to carbon dioxide accumulating in the low ravine from geothermal activity in the area.

7. ClO2

ANSWERS TO EXERCISES

1.. (a)) Homogeneous mixture.

(b)) Compound.

(c)) Element.

(d)) Heterogeneous mixture.

2.. (a) Heterogeneous mixture.

(b) Element.

(d) Compound.

3. About 65 g/100 g H2O.0

4.. About 280 g/100 g H20O (interpolated from graph).

5.. Unsaturated; about 240 g of sugar are soluble per 100 g H2O H20 at 40°C.

6.. Saturated; interpolation from graph shows that only about 130 g of NaNO03 are soluble in 100 g H2O H20 at 60°C.

7. (a)) S

(b)) Na

(c)) Al

8.. (a)) He

(b)) Ag

(c)) Cr

9. (a)) Nitrogen.

(b) Potassium.

(c)) Zinc.

10. (a)) Calcium.

(b)) Fluorine.

11.. (a)) 3, 2A

(b)) 4, 2B

(c)) 5, 4A

12. (a)) 2, 8A

(b)) 6, 2B

(c)) 5, 7A

13.. (a)) Representative, nonmetal, gas.

(b)) Transition, metal, solid.

(c)) Inner transition, metal, solid.

14.. (a)) Transition, metal, solid.

(b)) Representative, nonmetal, gas.

(c)) Representative, nonmetal, liquid.

15.. (a)) 14, 4, 3

(b)) 33, 5, 4

16.. (a)) 4, 2, 2

(b)) 16, 6, 3

17.. (a)) 6.94 u, 3, 3, 3

(b)) 197.0 u, 79, 79, 79

18.. (a)) 39.9 u, 18, 18, 18

(b)) 87.6 u, 38, 38, 38

19. (a)) 2

(b)) 2,8,3

20. (a) 2,1

(b) 2,8,5

21. (a)) Ca, Mn, Se

(b) Po, Se, O

22. (a) Na, P, Cl

(b) Br, Cl, F

23. (a)) Sr, Sn, Xe

(b) Ar, Ne, He

24. (a) Cs, K, Na

(b) Ca, As, Br

25. (a) Kr, Br, Ca

(b) Li, Rb, Cs

26. (a)) Ne, C, Be

(b) Si, Ge, Pb

27.. (a)) Sulfuric acid.

(b)) Nitric acid.

(c)) Hydrochloric acid.

28.. (a)) Phosphoric acid.

(b)) Acetic acid.

(c)) Carbonic acid.

29.. (a)) Calcium bromide.

(b)) Dinitrogen pentasulfide.

(c)) Zinc sulfate.

(d)) Potassium hydroxide.

(e)) Silver nitrate.

(f)) Iodine heptafluoride.

(g)) Ammonium phosphate.

(h)) Sodium phosphide.

30.. (a)) Aluminum carbonate.

(b)) Ammonium sulfate.

(c)) Lithium sulfide.

(d)) Sulfur trioxide.

(e)) Barium nitride.

(f)) Barium nitrate.

(g)) Silicon tetrafluoride.

(h)) Disulfur dichloride.

31.. Li2S, Li3N, LiHC0O3

32.. Ba(NO)2 BaCl2 Ba3(PO4)2

ANSWERS TO RELEVANCE QUESTIONS

11.1.Answers depend on the individual. Common answers will be water or salt for the compound, and air or coffee for the homogeneous mixture.

11.2.It is impossible to locate an item that is not composed of chemicals.

11.3.Helium is totally unreactive, and so there is no way to make it explode in the blimp.

ANSWERS TO VISUAL CONNECTION

a. pure substances b. compounds c. homogeneous