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6
2
2
2
8.10. (a) Argon: 1s 2s 2p 3s 3p 6 8.18. (a) Bromine gained an electron to acquire a 1– charge, so it
2
6
6
2
2
2
(b) Zinc: 1s 2s 2p 3s 3p 4s 3d 10 must be in family VIIA (the members of this family have
2
2
6
10
2
6
2
(c) Bromine: 1s 2s 2p 3s 3p 4s 3d 4p 5 seven electrons and need one more to acquire the noble
gas structure).
8.11. Atomic weight is the weighted average of the isotopes as they
(b) Potassium must have lost one electron, so it is in IA.
occur in nature. Th us,
(c) Aluminum lost three electrons, so it is in IIIA.
Lithium-6: 6.01512 u × 0.0742 = 0.446 u (d) Sulfur gained two electrons, so it is in VIA.
Lithium-7: 7.016 u × 0.9258 = 6.4054 u (e) Barium lost two electrons, so it is in IIA.
Lithium-6 contributes 0.446 u of the weighted average and (f) Oxygen gained two electrons, so it is in VIA.
lithium-7 contributes 6.4954 u. The atomic weight of lithium is 16 23 3 35

8.19. (a) O (b) Na (c) H (d) Cl

1
11
8
17
therefore
0.446 u
+6.4954 u CHAPTER 9
6.941 u 9.1.
8.12. Recall that the subscript is the atomic number, which identifi es
the number of protons. In a neutral atom, the number of
protons equals the number of electrons, so the atomic number

tells you the number of electrons, too. The superscript is the

mass number, which identifies the number of neutrons and the

number of protons in the nucleus. The number of neutrons is
therefore the mass number minus the atomic number.
Protons Neutrons Electrons
(a) 6 6 6
(b) 1 0 1
(c) 18 22 18
(d) 1 1 1
(e) 79 118 79
(f) 92 143 92
8.13. Period Family
(a) Radon (Rn) 6 VIIIA
(b) Sodium (Na) 3 IA
(c) Copper (Cu) 4 IB
(d) Neon (Ne) 2 VIIIA
(e) Iodine (I) 5 VIIA
(f) Lead (Pb) 6 IVA
8.14. Recall that the number of outer shell electrons is the same as
9.2. (a) Sulfur is in family VIA, so sulfur has six valence electrons
the family number for the representative elements:
and will need two more to achieve a stable outer structure
(a) Li: 1 (d) Cl: 7
like the noble gases. Two more outer shell electrons will
(b) N: 5 (e) Ra: 2 2+
give the sulfur atom a charge of 2–. Copper will balance
(c) F: 7 (f) Be: 2
the 2– charge of sulfur, so the name is copper(II) sulfi de.
8.15. The same information that was used in question 8.14 can be Note the -ide ending for compounds that have only two

used to draw the dot notation (see Figure 8.20): diff erent elements.
(a) B (c) Ca (e) O (b) Oxygen is in family VIA, so oxygen has six valence
electrons and will have a charge of 2–. Using the crossover
technique in reverse, you can see that the charge on the
oxygen is 2–, and the charge on the iron is 3–. Th erefore,
(b) Br (d) K (f) S the name is iron(III) oxide.
(c) From information in (a) and (b), you know that oxygen
8.16. The charge is found by identifying how many electrons are lost

has a charge of 2–. The chromium ion must have the same

or gained in achieving the noble gas structure:
(a) Boron 3+ (d) Potassium 1+ charge to make a neutral compound as it must be, so the
(b) Bromine 1– (e) Oxygen 2– name is chromium(II) oxide. Again, note the -ide ending
(c) Calcium 2+ (f) Nitrogen 3– for a compound with two diff erent elements.
(d) Sulfur has a charge of 2–, so the lead ion must have the
8.17. Metals have one, two, or three outer electrons and are located in same positive charge to make a neutral compound. Th e
the left two-thirds of the periodic table. Semiconductors are name is lead(II) sulfi de.

adjacent to the line that separates the metals and nonmetals. Look
at the periodic table on the inside back cover and you will see
(a) krypton—nonmetal (d) sulfur—nonmetal
(b) cesium—metal (e) molybdenum—metal
(c) silicon—semiconductor (f) plutonium—metal
E-23 APPENDIX E Solutions for Group A Parallel Exercises 665