What type of bond wou,qs l*/d9z3qbiak5kn*0 k8yys l 5 ta bnhs+,cld you expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecule v,xw8. 4vn1 gslsr v3q$ \text{CaCl}_2 $ could be formed.

  Does the $ \text{H}_2 $ molecule have a permanent dipole moment? Does $ \text{O}_2 $? Does $ \text{H}_2\text{O} $? Explain.

Although the molecule cbe3) n tue8whh-dx.7 $ \text{H}_3 $ is not stable, the ion $ \text{H}_3^+ $ is. Explain, using the Pauli exclusion principle.

The energy of a molecule can be divided into four categories. What are theyt //dsjlj9at7?

  Would you expect the m2mg,lkq t4 1sgolecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon at 6icx lnt+ svyf+v04v.he+w9kom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in a metal, why d9kc4j tngrue+cj:1- k on't they leave thk -jk9 c1nu:+ rj4gtcee metal entirely?

Explain why the resistivity lcxw uv+f19( kpn3.dp of metals increases with temperature whereas the resiwn+lupvc1p9 d.kx3 f( stivity of semiconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain h)f6, k5kpvk2szj(i rd ow the current is rectpkkk56(fj)rz vdis2, ified and how current flows during each half cycle.

Compare the resistan1j chidgyj6w42 l5v3rco9)zy ce of a pn junction diode connected in forward bias to its r3iho)1zr4 lj6gcwvc 2yj y d95esistance when connected in reverse bias.

Explain how a transistor could be used as a swx7i bb .efk5rih.h-b1itch.

What is the main difference between n-pyc o9::iv 4zdtype and p-type semiconductors?

Describe how a pnp transk:ld k hmi,61kistor can operate as an amplifier.

In a transistor, the base-emitteoi0b )cgtfk, 5r junction and the base-collector junction are essentially diodes. Are these junctions reverse-biased or forward-biased in the applicationc k)ofbtgi, 05 shown in (Fig. Below)?

A transistor can amplify an electronic signal, meanm(kem *t::ghoing it can increase the power of an input hmtm:o (ekg*:signal. Where does it get the energy to increase the power?

A silicon semiconductor is doped with phosphorus. Will thetg8km s(a, po,se atoms be donors or acceptors? What type of semicond k ,mt,osa(p8guctor will this be?

  Do diodes and transistors obey Ohm’s law? Explpz n(bv2ys9h)*7 q hflvu-sz 9ain. {yes|no}

  Can a diode be used to amplify a signal? Explainip w5 c evsd1bxo1y+bpt-/ x35. {yes|no}

  Estimate the binding ener9nih90smma tj4p* ;2mgn-u irgy of a KCl molecule by calculating the electrostatic potential esr-4ming2;n9au mhmi t9*jp 0nergy when the $ \text{K}^+ $ and $ \text{Cl}^- $ ions are at their stable separation of 0.28 nm. Assume each has a charge of magnitude $ 1.0e $. Binding energy =    eV

  The measured binding energy of KCl is yw7jh0tp rw00-,i shx hp(s b)4.43 eV. From the result of Problem 1, estimate the contribution to the binding energy of the repelling electron clouds at the equilibrium dista,0(hw7xht-) yssriw0 bj pp0h nce $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding enervlaocc-;- hm;a p-zf.gy of the $ \text{H}_2 $ molecule, assuming the two H nuclei are 0.074 nm apart and the two electrons spend 33% of their time midway between them. Binding energy =    eV

  Binding energies are often measured experimeg- yqnl(r-zn 3ntally in kcal per mole, and then the binding energy in eV per molecule is calculated from that result. What is the conversion factor in g- nnrq-z3l(yg oing from kcal per mole to eV per molecule? What is the binding energy of $ \text{KCl} (= 4.43\ \text{eV}) $ in kcal per mole?
We convert the units =    $\text{eV/molecule}$
For KCl we have =    $kcal/mol$

(a) Apply reasoning similar to that in the text for the states qd.n9 v04 3ahiyersb,l p,oh s3 2adc9in the formation of tyeis3l oqs0 a9ddh, c4hvb,ar.2p39nhe $ \text{H}_2 $ molecule to show why the molecule $ \text{He}_2 $ is not formed.
(b) Explain why the $ \text{He}_2^+ $ molecular ion could form. (Experiment shows it has a binding energy of 3.1 eV at )

Show that the quantit5pccl82 r-du7yfr rs*y $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic ro xv51d;ag ipuv28af)ytational energy,” $ \frac{\hbar^2}{2I} $ for $ \text{N}_2 $ is $ 2.48 \times 10^{-4}\ \text{eV} $. Calculate the $ \text{N}_2 $ bond length. $r = $    $ \times 10^{-10}\ \text{m}$

  (a) Calculate the characteristic ro3dfm2hlr nl y;t 8ptb.a 5,w:;zp l1rptational energy, $ \frac{\hbar^2}{2I} $ for the $ \text{O}_2 $ molecule whose bond length is 0.121 nm. $\frac{\hbar^2}{2I} =$    $ \times 10^{-4}\ \text{eV}$
(b) What are the energy and wavelength of photons emitted in a $ L=2 $ to $ L=1 $ transition? $\lambda $ =    mm

  The equilibrium separh 0mxbo1g-*(gbl/5sa4p5oop i 4tfw pation of H atoms in the $ \text{H}_2 $ molecule is 0.074 nm (Fig. Below). Calculate the energies and wavelengths of photons for the rotational transitions
(a) $ L=1 $ to $ L=0 $, $hf $ $=$    $ \times 10^{-2}\ \text{eV}$$\;\;\;\;$$\lambda $ =    mm
(b) $ L=2 $ to $ L=1 $, $hf $ $=$    $ \times 10^{-2}\ \text{eV}$$\;\;\;\;$$\lambda $ =    mm
(c) $ L=3 $ to $ L=2 $. $hf $ $=$    $ \times 10^{-2}\ \text{eV}$$\;\;\;\;$$\lambda $ =    mm

  Calculate the bond length for the NaCle;u +j 0;c fpcynxj71r molecule given that three successive wavelengths for rotational transit cfy07 c;rx;ju1p +ejnions are 23.1 mm, 11.6 mm, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) 9 x:ffp*bil inh90vkue *(d)gto estimate the stiffness constant $ k $ for the $ \text{H}_2 $ molecule. (Recall that $ PE = \frac{1}{2}kx^2 $) k =    N/m
(b) Then estimate the fundamental wavelength for vibrational transitions using the classical formula (Chapter 11), but use only the mass of an H atom (because both H atoms move).$\lambda$ =    $\mu m$

  The spacing between “nearest neighbor” Na and Cl ions in a NaCl crystal is 0.2g6v p8i;;vk 8nv sy,hm73pi ws4 nm.mgw,p8pi7;68shvnv yis3 vk; What is the spacing between two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a def 5i z*:gylop)nsity of $ 2.165\ \text{g/cm}^3 $. The molecular weight of NaCl is 58.44. Estimate the distance between nearest neighbor Na and Cl ions. [Hint: Each ion can be considered to have one "cube" or "cell" of side $ s $ (our unknown) extending out from it.] $s$ =    nm

  Repeat Problem 13 for KCl whose density ia tw5u3 m.si zwkl z0l,lg;4;ps $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chloris t;ajq9q. v.ide crystal is a good insulator. [Hint: Consider the shsaiq;.tv9 qj .ells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased frequency, begins to cf *35,g*fv9n)-v unvlyo ) :t ggssaoqonduct when the wavelength of light is 640 n)f 3ota:sfnvu95* *v qs-)gvy,gnl go m. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon that can cause an elen w1iceqpzo/.qzr /8*ctron in silicon ($ E_g = 1.14\ \text{eV} $) to jump from the valence band to the conduction band. $\lambda $ =    $\mu m$

  The energy gap between val gwa:okr-9*mczk;di-ence and conduction bands in germanium is 0.72 eV. What range of wavelengtogric -w;-a k mz:d9k*hs can a photon have to excite an electron from the top of the valence band into the conduction band? $\lambda \leq$    $ \ \mu\text{m}$

  The energy gap $ E_g $ in germanium is 0.72 eV. When used as a photon detector, roughly how many electrons can be made to jump from the valence to the conduction band by the passage of a 760-keV photon that loses all its energy in this fashion? N =    $ \times 10^6$

We saw that there are a .x7ccee5n ci8t.nu-;:nfuh$ 2N $ possible electron states in the 3s band of Na, where $ N $ is the total number of atoms. How many possible electron states are there in the
(a) 2s band,
(b) 2p band,
(c) 3p band?
(d) State a general formula for the total number of possible states in any given electron band.

  Suppose that a silicon semiconductor is doped withs- st3l63hi ug phosphorus so that one silicon atom in 6lsih 3-gtu 3s$ 10^6 $ is replaced by a phosphorus atom. Assuming that the "extra" electron in every phosphorus atom is donated to the conduction band, by what factor is the density of conduction electrons increased? The density of silicon is $ 2330\ \text{kg/m}^3 $, and the density of conduction electrons in pure silicon is about $ 10^{16}\ \text{m}^{-3} $ at room temperature. $\frac{N_{\text{doping}}}{N_{\ce{Si}}} = $    $ \times 10^6$

  At what wavelength will an LED radiate if +hypm:t0 4tag made from a material with an energy gapyp4g 0:h+ tmta $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wnav/qw3 ekqa 5 )wo2mw,n-x 8b* tquy9avelength $ \lambda = 650\ \text{nm} $, what is the energy gap (in eV) between valence and conduction bands? $e_g$ =    eV

  A silicon diode, whose current-voltage c5 rany:,6xqz rharacteristics are given in (Fig. Below), is connected in series witarqy6r,xn z:5 h a battery and a $ 960-\Omega $ resistor. What battery voltage is needed to produce a 12-mA current? $V_{\text{battery}}$=    V

  Suppose that the diode of (Figc . n.dqoh;2ayls1 7ul. Below) is connected in series to a $ 100-\Omega $ resistor and a 2.0-V battery. What current flows in the circuit? [Hint: Draw a line on (Fig. Below) representing the current in the resistor as a function of the voltage across the diode. The intersection of this line with the characteristic curve will give the answer.]    mA

Sketch the resistance as a function of current(g.kk3f 4awd o, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estimate very rough)md(mpq: a4f .5bi yskly the average current in the output rk)dq4mfay.mi :p (b5 sesistor $ R $ ($ 25\ \text{k}\Omega $) for
(a) a half-wave rectifier(Fig. Below a), $I_{av}$ =    mA
(b) a full-wave rectifier (Fig. Below b) without capacitor.$I_{av}$ =    mA

a

b

  A silicon diode passes significant current only if the forward-bias voltage /pldj3* . 1 m.+da7ma2tteo j, ztzowrexceeds about 0.6 V. Make a rough estimate of the average current inlzzowed.t2r pj mo,31/ t+j*a. da7mt the output resistor $ R $ of
(a) a half-wave rectifier (Fig. Below a),$I _{av}$ =    mA
(b) a full-wave rectifier (Fig. Below b) without a capacitor. Assume that $ R = 150\ \Omega $ in each case and that the ac voltage is 12.0 V rms in each case. $I _{av}$ =    mA
a
b

  A 120-V rms 60-Hz voltage is to be rectified with a full-wave rectifier (Fgujr6ig(bq0 9 ig. Below), wher6 gi0bjqu9( rge $ R = 21\ \text{k}\Omega $ and $ C = 25\ \mu\text{F} $.
(a) Make a rough estimate of the average current. $I_{av}$ =    mA(smooth)
(b) What happens if $ C = 0.10\ \mu\text{F} $?$I_{av}$ =    mA (rippled)

From !num!2%, write an equation for the relationship between the basr;zej*phsv8ix,xmi32(;( wrm91y0f wqvgq r e current $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energy of the e nalo.( v; v,i8gm5qwa.i*sf$ \text{H}_2 $ molecule by calculating the difference in kinetic energy of the electrons between when they are in separate atoms and when they are in the molecule, using the uncertainty principle. Take $ \Delta x $ for the electrons in the separated atoms to be the radius of the first Bohr orbit, 0.053 nm, and for the molecule take $ \Delta x $ to be the separation of the nuclei, 0.074 nm. [Hint: Let $ p \approx \Delta p \approx \hbar/\Delta x $]    eV

  The average translational kinetic energy of an att,favnt 9 -u*qom or molecule is about $ KE = \frac{3}{2}kT $ (Eq. 13-8), where $ k = 1.38 \times 10^{-23}\ \text{J/K} $ is Boltzmann's constant. At what temperature $ T $ will $ KE $ be on the order of the bond energy (and hence the bond likely to be broken by thermal motion) for
(a) a covalent bond of binding energy 4.5 eV (say $ \text{H}_2 $), $T =$    $ \times 10^4\ \text{K}$
(b) a "weak" hydrogen bond of binding energy 0.15 eV? $T = $    $ \times 10^3\ \text{K}$

  In the ionic salt KF, the separation distance between ions7w z8a k(3u d0daafmk( is about 0.27 nm.
(a) Estimate the electrostatic potential energy between the ions assuming them to be point charges (magnitude $ 1e $). PE =    eV
(b) It is known that F releases 4.07 eV of energy when it "grabs" an electron, and 4.34 eV is required to ionize K. Find the binding energy of KF relative to free K and F atoms, neglecting the energy of repulsion. Binding energy =   eV

  Consider a monoatomic solid with a weakly bound cubic9py df) pl-,s 6+lt3operi tu2 lattice, with each atom connected to six neighbors, each bond having a binding ener,o6eppf)ldt-y lps r93ut i+ 2gy of $ 3.9 \times 10^{-3}\ \text{eV} $. When this solid melts, its latent heat of fusion goes directly into breaking the bonds between the atoms. Estimate the latent heat of fusion for this solid, in $ \text{J/kg} $. [Hint: Show that in a simple cubic lattice (Fig. Below), there are three times as many bonds as there are atoms, when the number of atoms is large.]$L_{\text{fusion}} =$    $\times 10^4\ \text{J/kg}$

  For $ \text{O}_2 $ with a bond length of 0.121 nm, what is the moment of inertia about the center of mass? I =    $\times 10^{-46}\ \text{kg·m}^2$

A diatomic molecule is found to have an activation energy of 1.4 eV. xq9vx7jx5wjgwhj4t )n;y h 07 When the molecule is disassociated, 1.6 eV of energy is released. Draw a potential energw0h7y)j 57x4gwx;v xhjjtq 9ny curve for this molecule.

  When EM radiation is incident on diamond, it is -rkn(scyt j69v1 u9jt found that light with wavelengths shorter than 226 nm wily9n(-jtc9t 61r vuj ksl cause the diamond to conduct. What is the energy gap between the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emits Il gv 6q*39 .fkrn.zjpkR light. If the detector on the TV set is not to react to visible light, could it make use of si9jg. fl.rz3p6* kknvq licon as a "window" with its energy gap $ E_g = 1.14\ \text{eV} $? $\lambda $ =    $\mu m$
What is the shortest-wavelength light that can strike silicon without causing electrons to jump from the valence band to the conduction band?

  For an arsenic donor atom in a doped silicon semiconductor, uwf 6 182lnwrgassume that the "extra" electron moves in a Bohr orbit about 26rg lf1w wnu8the arsenic ion. For this electron in the ground state, take into account the dielectric constant $ K = 12 $ of the Si lattice (which represents the weakening of the Coulomb force due to all the other atoms or ions in the lattice), and estimate
(a) the binding energy, E =    eV
(b) the orbit radius for this extra electron. r =    nm

  Most of the Sun's radiation has wavelengths shorter thanmu;ueu304ixg bb oosgw*0 m.; 1000 nm. For a solar cell to absorb all this, what energy gap ought w.bomsiguu4gm;3;b ue0x0*othe material have? $E_g$ =    eV

  For a certain semiconductor, then52kbnx2d ;1(t5 + pz lddnmwa longest wavelength radiation that can be absorbed is 1.92 mm. What is the energy gap in this semiconductor? d nka5;12b n5dxw+ 2l zdtpn(m $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs were first devel m(:n*8eo2q:gqdfli e oped. Approximately what energy gaps would you expect to find in green (525 nm) and in blue (465 nm) LEDs qoi:fd ml8genq (*2:e?
the green $E_g$ =    eV
the blue $E_g$ =    eV

  A zener diode voltage regulator is shown in (Fig. Below). Suppose thatm .p(/:znyk rw $ R = 1.80\ \text{k}\Omega $ and that the diode breaks down at a reverse voltage of 130 V. (The current increases rapidly at this point, as shown on the far left of Fig. 29-28 at a voltage of $ -12\ \text{V} $ on that diagram.) The diode is rated at a maximum current of 120 mA.
(a) If $ R_{\text{load}} = 15.0\ \text{k}\Omega $, over what range of supply voltages will the circuit maintain the output voltage at 130 V?   $\ \text{V} \leq V \leq $    $\ \text{V}$
(b) If the supply voltage is 200 V, over what range of load resistance will the voltage be regulated?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$