Basics ‹ 67
Give yourself 1 point for the effective nuclear charge, and give yourself 1 point for
the remainder of the discussion.
(b) The electron configurations are Fe 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6 , Fe2+ 1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 ,
and Fe^3 + 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5. It is possible to condense the configurations to
Fe [Ar]4s^2 3d^6 , Fe^2 + [Ar]3d^6 , and Fe^3 + [Ar]3d^5. Do not forget that electrons from the
outer shell are always removed first. For iron, the outer shell is 4.
Give yourself 1 point for each correct electron configuration.
(c) When moving across a period on the periodic table, the value of the effective nuclear
charge increases with atomic number. This causes a general increase from Li to Be to
B. DO NOT use the argument that ionization energies increase to the right on the
periodic table unless you also discuss effective nuclear charge.
The even higher value of Be (greater than B) is due to the increased stability of the
electron configuration of Be. Beryllium has a filled s-subshell. Filled subshells have an
increased stability, and additional energy is required to pull an electron away.
Give yourself 0 points if you say that the ionization energy increases to the right
on the periodic table. This is an observation, not an explanation. The effective nuclear
charge argument is worth 1 point. Give yourself 1 more point for the filled subshell
discussion.
(d) The effective nuclear charge in F is greater than the effective nuclear charge in O. This
causes a greater attraction of the electrons. DO NOT use the argument that electron
affinity increases to the right on the periodic table unless you also discuss effective
nuclear charge.
You get 1 point for the effective nuclear charge answer.
(e) Because all these solids adopt the same structure, the structure is irrelevant. The sizes of
the anions are similar; thus, anion size arguments are not important. Two factors, other
than structure and anion size, are important here. The two compounds with the highest
lattice energies contain divalent ions (+2 or –2), whereas NaF contains univalent ions
(+1 or –1). The higher the charge is, the greater the attraction between the ions is. The
lattice energy increases as the attraction increases.
The difference between the CaO and BaO values occurs because the larger the ion
is, the lower the attraction is (greater separation). The lower attraction leads to a lower
lattice energy.
You get 1 point for correctly discussing the charges. A correct size argument will
get you 1 more point.
Total your points. There are 10 points possible.❯ Rapid Review
Here is a brief review of the most important points in the chapter. If something sounds
unfamiliar, study it in the chapter and your textbook.
● Know the metric measurement system and some metric/English conversions.
● Know how to convert from any one of the Fahrenheit/Celsius/Kelvin temperature scales
to the other two.
● The density of a substance is mass per unit volume.
● Know how to determine the number of significant figures in a number, the rules for how
many significant figures are to be shown in the final answer, and the round-off rules.