09_Petrucci10e_SSM - CHAPTER 9 THE PERIODIC TABLE AND SOME...

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201 CHAPTER 9 THE PERIODIC TABLE AND SOME ATOMIC PROPERTIES PRACTICE EXAMPLES 1A Atomic size decreases from left to right across a period, and from bottom to top in a family. We expect the smallest elements to be in the upper right corner of the periodic table. S is the element closest to the upper right corner and thus should have the smallest atom. S = 104 pm As = 121 pm I = 133 pm 1B From the periodic table inside the front cover, we see that Na is in the same period as Al (period 3), but in a different group from K, Ca, and Br (period 4), which might suggest that Na and Al are about the same size. However, there is a substantial decrease in size as one moves from left to right in a period due to an increase in effective nuclear charge. Enough in fact, that Ca should be about the same size as Na. 2A Ti 2+ and V 3+ are isoelectronic; the one with higher positive charge should be smaller: V 3+ < Ti 2+ . Sr 2+ and Br are isoelectronic; again, the one with higher positive charge should be smaller: Sr Br . In addition Ca and Sr both are ions of Group 2A; the one of lower atomic number should be smaller. Ca Sr Br . Finally, we know that the size of atoms decreases from left to right across a period; we expect sizes of like- charged ions to follow the same trend: Ti Ca . The species are arranged below in order of increasing size. V pm Ti pm Ca pm Sr pm Br pm 3+ 64 86 100 113 196 bg b g b g b g  2B Br - clearly is larger than As since Br is an anion in the same period as As. In turn, As is larger than N since both are in the same group, with As lower down in the group. As also should be larger than P, which is larger than Mg , an ion smaller than N. All that remains is to note that Cs is a truly large atom, one of the largest in the periodic table. The As atom should be in the middle. Data from Figure 9-8 shows: 65 70 125 196 265 pm for Mg pm for N pm for As pm for Br pm for Cs 3A Ionization increases from bottom to top of a group and from left to right through a period. The first ionization energy of K is less than that of Mg and the first ionization energy of S is less than that of Cl. We would expect also that the first ionization energy of Mg is smaller than that of S, because Mg is a metal.
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Chapter 9: The Periodic Table and Some Atomic Properties 202 3B We would expect an alkali metal (Rb) or an alkaline earth metal (Sr) to have a low first ionization energy and nonmetals (e.g., Br ) to have relatively high first ionization energies. Metalloids (such as Sb and As) should have intermediate ionization energies. Since the first ionization energy for As is larger than that for Sb, the first ionization energy of Sb should be in the middle. 4A Cl and Al must be paramagnetic, since each has an odd number of electrons. The electron configurations of K + ([Ar]) and O 2 ([Ne]) are those of the nearest noble gas. Because all of the electrons are paired, they are diamagnetic species. In Zn: [Ar] 3 4 10 2 ds all electrons are paired and so the atom is diamagnetic.
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This note was uploaded on 11/07/2011 for the course CHEMISTRY 1500 taught by Professor Hammedmirza during the Fall '11 term at York University.

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09_Petrucci10e_SSM - CHAPTER 9 THE PERIODIC TABLE AND SOME...

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