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Unformatted text preview: Chemistry 209 Homework #6 answers Chapter 9: 8 Element 112 should appear at the end of the sequence of filling d orbitals in period 7; the element below Bi, which would presumably resemble it chemically, should appear as element 115 (including 32 additional charges, and 32 electrons, distributed 2 in 7 s , 6 in 6 p and 7 p , 10 in 6 d and 14 in the 5 f orbitals); a noble gas should appear with Z 32 larger than in Radon, or at 118. 16 Atomic radius increases we go from nonmetals to metals, and as we go to larger values of n . Iodine has a larger n value than Al, but Al is more metallic. So the two effects work in opposite directions, and no general argument can inform us as to the specifics. Figure 9-8 tells us that Al (143 pm) is slightly larger than I (133 pm); those as ions, Al 3+ (53 pm) is massively smaller than is I (220 pm). 36 The electron configuration for Fe metal is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 6 . When it loses 2 electrons the first ion formed is Fe 2+ with electron configuration 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 6 ; and Fe 3+ has configuration 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 5 . While the 4 s electrons are lower energy, and fill before, the 3 d states, they are higher energy in most of the transition metal ions. Thus we expect 6 d electrons in Fe 2+ ; by Hunds rule that corresponds to 4 unpaired electrons and one paired set, and in Fe 3+ there are 5 unpaired electronsone per d orbital. 40 (a) Naively Id look for the metal with largest n ; that would appear to be Ba. Look at figure 9-8; it doesnt get down as far as Id like, so well settle for figure 9-4. Ba should be right next to Cs; the only atoms that look bigger are K, Rb and maybe Sr. So Ill vote for Ba. (b) First ionization energies are lowest for alkali metals, and the larger ones at that. Mg is closest to the alkali metals, though we saw in class that its first IE is higher than that of Al; as Al is taking an electron out of of p orbital, Mg from an s orbital. Id vote for Al...figure 9-9 suggests that only the alkali metals are lower than Al.Al....
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- Fall '07