Page 76 - Materials Science and Engineering An Introduction

48 • Chapter 2 / Atomic Structure and Interatomic Bonding

QUESTIONS AND PROBLEMS

Problem available (at instructor’s discretion) in WileyPLUS
Fundamental Concepts The Periodic Table
Electrons in Atoms 2.11 With regard to electron configuration, what do
2.1 Cite the difference between atomic mass and all the elements in Group IIA of the periodic ta-
atomic weight. ble have in common?
2.2 Silicon has three naturally occurring isotopes: 2.12 To what group in the periodic table would an ele-
28
92.23% of Si, with an atomic weight of 27.9769 ment with atomic number 112 belong?
amu; 4.68% of 29 Si, with an atomic weight of 2.13 Without consulting Figure 2.8 or Table 2.2, de-
28.9765 amu; and 3.09% of 30 Si, with an atomic termine whether each of the following electron
weight of 29.9738 amu. On the basis of these data, configurations is an inert gas, a halogen, an alkali
confirm that the average atomic weight of Si is metal, an alkaline earth metal, or a transition
28.0854 amu. metal. Justify your choices.
2
2.3 Zinc has five naturally occurring isotopes: 48.63% (a) 1s 2s 2p 3s 3p 5
2
2
6
64
of Zn, with an atomic weight of 63.929 amu; 2 2 6 2 6 7 2
27.90% of 66 Zn, with an atomic weight of 65.926 (b) 1s 2s 2p 3s 3p 3d 4s
6
2
10
2
2
6
2
amu; 4.10% of 67 Zn, with an atomic weight of (c) 1s 2s 2p 3s 3p 3d 4s 4p 6
66.927 amu; 18.75% of 68 Zn, with an atomic (d) 1s 2s 2p 3s 3p 4s 1
6
2
2
2
6
weight of 67.925 amu; and 0.62% of Zn, with an 2 2 6 2 6 10 2 6 5 2
70
atomic weight of 69.925 amu. Calculate the aver- (e) 1s 2s 2p 3s 3p 3d 4s 4p 4d 5s
6
2
2
age atomic weight of Zn. (f) 1s 2s 2p 3s 2
2.4 Indium has two naturally occurring isotopes: In, 2.14 (a) What electron subshell is being filled for the
113
with an atomic weight of 112.904 amu; and 115 In, rare earth series of elements on the periodic table?
with an atomic weight of 114.904 amu. If the aver- (b) What electron subshell is being filled for the
age atomic weight for In is 114.818 amu, calculate actinide series?
the fraction-of-occurrences of these two isotopes.
2.5 (a) How many grams are there in one amu of a Bonding Forces and Energies
material? 2.15 Calculate the force of attraction between a Ca
2
2
(b) Mole, in the context of this book, is taken and an O ion whose centers are separated by a
in units of gram-mole. On this basis, how many distance of 1.25 nm.
atoms are there in a pound-mole of a substance? 2.16 The atomic radii of Mg and F ions are 0.072

2
2.6 (a) Cite two important quantum-mechanical con- and 0.133 nm, respectively.
cepts associated with the Bohr model of the atom. (a) Calculate the force of attraction between
(b) Cite two important additional refinements these two ions at their equilibrium interionic sepa-
that resulted from the wave-mechanical atomic ration (i.e., when the ions just touch one another).
model. (b) What is the force of repulsion at this same
2.7 Relative to electrons and electron states, what separation distance?
does each of the four quantum numbers specify? 2.17 The force of attraction between a divalent cation
8
2.8 For the K shell, the four quantum numbers for and a divalent anion is 1.67 10 N. If the ionic
each of the two electrons in the 1s state, in the radius of the cation is 0.080 nm, what is the anion
1
1
order of nlm l m s , are 100 and 100(- ). Write the radius?
2
2
four quantum numbers for all of the electrons in 2.18 The net potential energy between two adjacent
the L and M shells, and note which correspond to ions, E N , may be represented by the sum of
the s, p, and d subshells. Equations 2.9 and 2.11; that is,
2.9 Give the electron configurations for the following
ions: P , P , Sn , Se , I , and Ni . E N = - A + B (2.17)
2

2
3
4
5
r r n
2.10 Potassium iodide (KI) exhibits predominantly ionic
bonding. The K and I ions have electron struc- Calculate the bonding energy E 0 in terms of the pa-
tures that are identical to which two inert gases? rameters A, B, and n using the following procedure: