ANSWERS TO MATCHING QUESTIONS
a. 12 b. 14 c. 13 d. 21 e. 18 f. 1 g. 7 h. 10 i. 2 j. 3 k. 23 l. 25
m. 24 n. 22 o. 4 p. 8 q. 16 r. 15 s. 6 t. 5 u. 19 v. 11 w. 9 x. 17 y. 20
ANSWERS TO MULTIPLE-CHOICE QUESTIONS
1. b 2. c 3. a 4. b 5. d 6. c 7. c 8. c 9. b 10. d 11. a 12. c
ANSWERS TO FILL-IN-THE-BLANK QUESTIONS
1. Organic chemistry 2. solvent 3. more 4. experimentation 5. molecules 6. aluminum
7. O3 8. Mendeleev 9. four 10. increases 11. nitrate 12. sodium hydroxide
ANSWERS TO 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.
3. 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.
4. Heterogeneous mixture
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.
7. Compounds can be prepared from, and decomposed into, elements by chemical
processes only.
8. An appropriate set of examples would be: bronze, salt water, air.
9. Water is the solvent, and sugar is the solute. When no more sugar dissolves, the
solution is saturated.
10. Any six of these: gold, silver, lead, copper, tin, iron, carbon, sulfur, antimony,
arsenic, bismuth, or mercury. Most of these are metals. The first gases isolated were
hydrogen, oxygen, nitrogen, and chlorine.
11. The first synthetic element, technetium (Tc) was produced by nuclear bombardment
of molybdenum with deuterons.
12. At present, about 118 elements are known, 88 of which occur naturally on Earth.
13. (a) Oxygen and silicon. (b) Iron and nickel. (c) Oxygen and carbon.
(d) Nitrogen and oxygen. (e) Hydrogen and helium.
14. The shapes of the allotropes of carbon are: tetrahedral, planar, and fullerene.
15. Dmitri Mendeleev developed the periodic table in 1869.
16. 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.
17. Periodic characteristics of elements include: 1) atomic number, 2) electron
configuration, 3) valence electrons, 4) atomic sizes, and 5) ionization energy. One can
also include metallic character in this list.
18. (a) Periods. (b) Groups.
19. The valence electrons are the ones that form chemical bonds.
20. (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.
21. Metallic character (a) decreases from left to right across a period, and (b) increases
down a group.
22. Semi-metals are those elements that display both metallic and nonmetallic
characteristics (i.e. they only conduct electricity under certain conditions). Examples are
boron, silicon, and germanium; they are typically used in the semiconductor industry for
electrical circuits.23.
Mercury and bromine are liquid. Hydrogen, oxygen, nitrogen, fluorine, and chlorine,
(plus six noble gases) are gases.
24. Atomic size (a) decreases from left to right across a period, and (b) increases down a
group.
25. NH3 – ammonia, HCl – hydrochloric acid, OH- - hydroxide, SO42-- sulfate
26. (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.
27. The Greek prefixes designate the number of atoms of the element that occur in the
molecule.
28. Because they have the same number of valence electrons.
29. Noble gases have interesting properties in that they are not very reactive. That is, it is
monotonic, and it does not bond easily with other elements. Their valence electron shells
are completely full, and thus are stable. They have very low melting and boiling points.
Noble gases are used in lighting in two ways: they are used in incandescent bulbs to
insulate the hot tungsten filament from other reactive gases, and they can be used in
“neon” signs giving an emission spectrum.
30. Fluorine and chlorine are gases, bromine is liquid, and iodine is solid. Fluorine is the
most reactive element.
31. Sodium iodide is added to prevent thyroid problems due to iodine deficiency.
32. NaHCO3 is baking soda.
33. Common uses for alkaline earth metals and their compounds include: safety flares,
metal alloys, medicines, acid neutralizers, road materials, chalk, and colors and dyes.
34. Hydrogen has properties of a nonmetal, but it can react like an alkali metal. It can also
react like a halogen. It is useful as a fuel source.
ANSWERS TO APPLYING-YOUR-KNOWLEDGE QUESTIONS
1. Element 118 would belong to Group 8A and Group 7 – it would resemble the noble
gases. Element 116 would belong to Group 6A and Group 7 – it would resemble elements
like oxygen, sulfur, and polonium.
2. The letter J.
3. 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.
4. Graphite makes a good lubricant because of its slipperiness, so the key should turn
easily.
5. Being “snobs” refers to the noble gases’ lack of chemical reactivity, or “interaction,”
with other elements.
6. Fluorine is the most reactive element of all and thus is so dangerous that it should be
handled only by experts.
6. For this hypothetical case, Ca-20 would have 20 protons and 10 electrons. No, neutral
hydrogen needs 1 proton and 1 electron, each with the same charge.
7. ClO2
ANSWERS TO EXERCISES
1. (a) Homogeneous mixture. (b) Compound. (c) Element. (d) Heterogeneous mixture.
2. (a) Heterogeneous mixture. (b) Element. (c) Homogeneous mixture. (d) Compound.
3. About 65 g/100 g H2O.
4. About 2½ times (interpolated from graph).
5. Unsaturated; about 240 g of sugar are soluble per 100 g H2O at 40°C.
6. Saturated; interpolation from graph shows that only about 130 g of NaNO3 are soluble
in
100 g H2O at 60°C.
7. (a) S (b) Na (c) Al
8. (a) Li (b) Pb (c) Xe
9. (a) Nitrogen. (b) Potassium. (c) Zinc.
10. (a) Barium. (b) Tungsten. (c) Tin.
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, LiHCO3
32. Ba(NO)2 BaCl2 Ba3(PO4)2