Chemistry and Honors Chemistry
Chapter 5 - The Periodic Law
Answers to Chapter Problems
2. The physical and chemical properties of the elements are periodic functions of their atomic numbers.
3. Groups of elements exhibit similar chemical and physical properties and behavior.
4. a. Generally, the configurations of the outermost electron shells of elements within the same group are the same.
There are a number of exceptions to this rule, however, among the transition elements.
4.b. Their outer shells are completely filled.
5. The length of a period is determined by the total number of electrons that can fill the outer sublevels of the elements of
that period.
6. An element’s period corresponds to its highest occupied main energy level.
7. a. the type of sublevel being filled in successive elements of that block
7. b. s-block: Groups 1 and 2; p-block: Groups 13–18 (except for He); d-block: Groups3–12 (except for the f-block
elements); f-block: those elements of the sixth and seventh periods between Groups 3 and 4
11. the transition elements
13. a. the Group 17 elements
13. b. The halogens are the most-reactive nonmetals; they react vigorously with most metals to form salts. They are also
among the most electronegative elements.
14. a. B, Si, Ge, As, Sb, Te
14. b. The metalloids are mostly brittle solids with electrical conductivities intermediate between those of metals (good
conductors) and nonmetals (nonconductors).
15. the lanthanides and the actinides
16. a. the elements of the s and p-blocks (plus hydrogen and helium)
16. b. decrease in atomic size, increase in ionization energy, increase in electron affinity, decrease in cationic size,
decrease in anionic size, increase in electronegativity
1
17. a. [He]2s , second period
2
4
17. b. [He]2s 2p , second period
10
1
17. c. [Ar]3d 4s , fourth period
10
2
5
17. d. [Ar]3d 4s 4p , fourth period
10
2
2
17. e. [Kr]4d 5s 5p , fifth period
18. a. third period, p-block, Group 16
18. b. fifth period, p-block, Group 14
18. c. sixth period, p-block, Group 17
19. a. Group 2, second period, s-block, Be
19. b. Group 1, third period, s-block, Na
19. c. Group 2, fifth period, s-block, Sr
19. d. Group 2, fourth period, s-block, Ca
19. e. Group 6, fourth period, d-block, Cr
22. a. one half the distance between the nuclei of two bonded identical atoms
22. b. They decrease.
22. c. As electrons are added to s and p sublevels in the same main energy level, the increasing positive charge of the
nucleus pulls electrons closer to the nucleus, resulting in decreasing atomic radii.
23. a. They generally increase.
23. b. Down a group, the outer electrons of each element occupy comparable sublevels in successively higher main
energy levels farther from the nucleus.
24. a. a charged atom or a charged group of bonded atoms
24. b. any process that results in the formation of an ion
24. c. the energy required to remove one electron from a neutral atom of an element
+
24. d. the energy required to remove an electron from a 1 ion
25. a. They increase across a period and decrease down a group.
25. b. Across a period, the increasing nuclear charge attracts electrons in the same energy level more
strongly and makes them more difficult to remove. Down a group, the electrons to be removed from each successive
element are farther from the nucleus in increasingly higher energy levels and are thus more easily removed.
26. a. the energy taken in or given off when an electron is added to an atom
26. b. Electron affinity values are either negative or positive. A negative sign indicates that energy is given off; a positive
sign indicates that energy is taken in.
27. a. A cation is a positive ion, and an anion is a negative ion.
27. b. Cations are always smaller than the atoms from which they are formed; anions are always larger.
28. a. Valence electrons are atomic electrons available to be lost, gained, or shared in the formation of chemical
compounds.
28. b. Valence electrons are located in an atom’s outermost energy level.
29. a. lost, 1
29. b. lost, 2
29. c. lost, 3
29. d. gained, 2
29. e. gained, 1
29. f. neither lost nor gained, 0
30. a. Electronegativity is the ability of an atom in a chemical compound to attract electrons from other atoms.
30. b. Fluorine is the most electronegative element and is arbitrarily assigned an electronegativity of 4.0. The values for all
other elements are assigned in relation to this value.
31. Most-electronegative: Group 17, least-electronegative: Group 1
32. Gold; atomic radii decrease across a period, and gold is farthest to the right in the sixth period, in which all 3 elements
are found.
33. a. First ionization energy is the energy required to remove one electron from an atom which is neutral. Second
+
ionization energy is the energy required to remove an electron from a 1 ion. Third ionization energy is the energy required
+
to remove an electron from a 2 ion.
33. b. Each successive ionization energy is larger than the preceding one.
33. c. Each successive electron must be removed from a particle with a greater positive charge.
34. In order of decreasing electron affinities, the elements are F, O, C, Li, Na, and Rb.
35. a. Ne, F, O, C, Li, K
35. b. Li and K would have the highest second ionization energies, because in both cases the second electron must come
from a completely filled noble-gas electron configuration. Of the two, Li would have the higher second ionization energy,
+
+
because the Li ion is smaller than the K ion.
2+
36. a. K
236. b. O
37. O; Group 16
2+
38. Ca ; because of the greater attraction that its 20 protons exert on the 18 electrons
39. a. seventh period, s-block, Group 1
39. b. fourth period, d-block, Group 4
39. c. fifth period, d-block, Group 11
39. d. sixth period, d-block, Group 10
40. a. the Group 18 elements
40. b. They are very unreactive.
+
41. Ca
42. a. 18
42. b. 7
42. c. the s and p-blocks
2
43. a. [Ne]3s , third period, Group 2
2
3
43. b. [Ne]3s 3p , third period, Group 15
1
2
43. c. [Ar]3d 4s , fourth period, Group 3
1
2
43. d. [Kr]4d 5s , fifth period, Group 3
47. In doing so, they achieve a noble-gas configuration.
49. Chlorine and potassium are reactive elements, whereas argon is unreactive. Chlorine readily gains one electron to
achieve the configuration of argon, and potassium readily loses one electron to achieve the argon configuration.