University Physics Volume 3

83 .

Potassium fluoride (KF) is a molecule formed by an ionic bond. At equilibrium separation the atoms are $r0=0.255nmr0=0.255nm$ apart. Determine the electrostatic potential energy of the atoms. The electron affinity of F is 3.40 eV and the ionization energy of K is 4.34 eV. Determine dissociation energy. (Neglect the energy of repulsion.)

84 .

For the preceding problem, sketch the potential energy versus separation graph for the bonding of $K+andFl−K+andFl−$ ions. (a) Label the graph with the energy required to transfer an electron from K to Fl. (b) Label the graph with the dissociation energy.

85 .

The separation between hydrogen atoms in a $H2H2$ molecule is about 0.075 nm. Determine the characteristic energy of rotation in eV.

86 .

The characteristic energy of the $Cl2Cl2$ molecule is $2.95×10−5eV2.95×10−5eV$. Determine the separation distance between the nitrogen atoms.

87 .

Determine the lowest three rotational energy levels of $H2.H2.$

88 .

A carbon atom can hybridize in the $sp2sp2$ configuration. (a) What is the angle between the hybrid orbitals?

89 .

List five main characteristics of ionic crystals that result from their high dissociation energy.

90 .

Why is bonding in $H2+H2+$ favorable? Express your answer in terms of the symmetry of the electron wave function.

91 .

Astronomers claim to find evidence of $He2He2$ from light spectra of a distant star. Do you believe them?

92 .

Show that the moment of inertia of a diatomic molecule is $I=μr02I=μr02$, where $μμ$ is the reduced mass, and $r0r0$ is the distance between the masses.

93 .

Show that the average energy of an electron in a one-dimensional metal is related to the Fermi energy by $E−=12EF.E−=12EF.$

94 .

Measurements of a superconductor’s critical magnetic field (in T) at various temperatures (in K) are given below. Use a line of best fit to determine $Bc(0).Bc(0).$ Assume $Tc=9.3K.Tc=9.3K.$

T (in K) $Bc(T)Bc(T)$
3.0 0.18
4.0 0.16
5.0 0.14
6.0 0.12
7.0 0.09
8.0 0.05
9.0 0.01
Table 9.6
95 .

Estimate the fraction of Si atoms that must be replaced by As atoms in order to form an impurity band.

96 .

Transition in the rotation spectrum are observed at ordinary room temperature ($T=300KT=300K$). According to your lab partner, a peak in the spectrum corresponds to a transition from the $l=4l=4$ to the $l=1l=1$ state. Is this possible? If so, determine the momentum of inertia of the molecule.

97 .

Determine the Fermi energies for (a) Mg, (b) Na, and (c) Zn.

98 .

Find the average energy of an electron in a Zn wire.

99 .

What value of the repulsion constant, n, gives the measured dissociation energy of 158 kcal/mol for CsCl?

100 .

A physical model of a diamond suggests a BCC packing structure. Why is this not possible?

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