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Unformatted text preview: 2.1 (a) When two or more atoms of an element have different atomic masses, each is termed an isotope.
(b) The atomic weights of the elements ordinarily are not integers because: (1) the atomic
masses of the atoms generally are not integers (except for 12C), and (2) the atomic weight is taken as the weighted average of the atomic masses of an atom's naturally occurring isotopes. 2.8 The Cs+ ion is just a cesium atom that has lost one electron; therefore, it has an electron conﬁguration the same as xenon The BF ion is a bromine atom that has acquired one extra electron; therefore, it has an electron conﬁguration the same as krypton. 2.13 (a) Differentiation of Equation (2.11) yields &_ A n3 _0
m WWW (b) How, solving for r (2 r0) A_ nB
o 0 Of A 11:11 — n}
rs = (a) (c) Substitution for r.3 into Equation (2.11} and solving for E (= E0) A B
0 r0 '1; A B ' i1fi1—n)+ infU—n}
(n3) (n8) 2.18 Covalently bonded materials are less dense than metallic or ionicallyr bonded ones because
covalent bonds are directional in nature whereas metallic and ionic are not; when bonds are
directional, the atoms cannot pack together in as dense a manner, yielding a lower mass
density. 2.21 For germanium, having the valence electron structure 4s£4pz, N' = 4; thus, there are 8 — N' = 4
covalent bonds per atom.
For phosphorus, having the valence electron structure 3523p3, N' = 5; thus, there are 8
— N' = 3 covalent bonds per atom. For selenium, having the valence electron structure 4324p4 N' = 6; thus, there are 8 — N' = 2 covalent bonds per atom. For chlorine, having the valence electron structure 3523;)5, N' = T; thus, there is 8 — N' = 1 covalent bond per atom. ...
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- Spring '10