What type of bond woul:(m8y lf1s uhed you expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecu dicc7k 8vw+w6le $ \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 bv/j g4 qia4im/dn5rxuc4 k ;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 aq1+o q*se;)ylxhb a/ u3pu2q5 vvq(ddre they?

  Would you expect the a5akkvbu8r+ i0 q)hv1molecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon atli- *b5ihq x 2vcfs7:5d)gs it z,vg7nom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons aq-pov3 za*d v:m++t/mkaou 1 fre free to roam about in a metal, why don't they leave the metal entdztq1k vvu fo-+p*:+3a mao/m irely?

Explain why the resistivity of metal h ;1dghr+g2v;0jbnax8izm3v i:8c2sy7u wre s increases with temperature whereas the resistivity of semiconductors may decrease with w 7i+0 2v;j:b8 3mhge8gsx zva1c2dy; rniurh increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Expla1wrob06jy g8e in how the current is rectified aer1wgo6 8b 0yjnd how current flows during each half cycle.

Compare the resistance of a pn junction diod uh3u5d98 pezq,:( esg/mqmmwe connected in forward bias to its resistanc d,:muz53pe(qqm/hg mweu8 9se when connected in reverse bias.

Explain how a transistoroe:h5h: e2;;sz msldc could be used as a switch.

What is the main difference between n-type and p-type2c3g9l*2hk14bls- 2w ,plqmd ge cioe semiconductors?

Describe how a pnp transistor can operate as an amp:e4j fi g,hmc,lifier.

In a transistor, the base-emitter junction and the base-collector junction ar (iegxd-ljm5 7e essentially diodes. Are these junctions reverse-biased or forward-biased in the application shown in (Fig. Below lid mxj-e57g()?

A transistor can amplify an electroniccmoekx +d9w4 7pe-6m r signal, meaning it can increase the power of an input signal. Where does it get the ener6we-9cmo e d 4+pmkr7xgy to increase the power?

A silicon semiconductor is doped wi dkqx; mjj,s2 1n,ya)nth phosphorus. Will these atoms be donors or acceptors? What type of semiconductor will s; n2 ,a )xnqmyj,1djkthis be?

  Do diodes and transistorshdf--pweqp, :bx/cli )x o83f obey Ohm’s law? Explain. {yes|no}

  Can a diode be used to amplify a signal? Exp hiamlbpq *m*qu ,6)x9lain. {yes|no}

  Estimate the binding energy of a Kw6fu-h,lrg- o Cl molecule by calculating the electrostatic potential energy ,r--gwlo6hfuwhen 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 4.43 eV. From the result of Probljm4 ytdja53, fem 1, estimate the contribution to the binding energy of the repelling electron clouds at the equilibm, 3jyf5dt aj4rium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energeif2,-r,/sm uy8 vlg iy 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 experimentally in kcal per mole, and then (px.b6is6m j8f. omrd g +jek:the binding energy in eV per molecule is calculated from that result. What is the conversion factor in going fromb.e o f mgpris(.xkj+6d:m86j 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 i(je30 uq wijwqg0 cg0,n the text for the states in the formation of, qc ejw0ui0wq gg3(j0 the $ \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 quantity6/vempyh2ir* ri p+a:z1mc -j $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “charac- 82e,g osqy;(. 3do ghumhslzteristic rotational 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 rotati*f sjg q i1)bka;,nbh0onal 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 separation of H atoms in the q+ hg9:7ln:dg j5/zioo*mfox$ \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 NaCl molecule given that three successive wav 3pyu17euglr3 :4b1pq,qbn zxelengths for rotational transitions are 23.1 mm, 11.6 mm, and 73nu g 1 qpu,yl3b1pz7xerb 4:q.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) to estimate t16;*:wkzpd vce*zx o(q x m((mqndt l+he 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 i v8 qrrx 7z0(lsc:s8bvs 0.24 nm. What is the spacing between two nearest neighbor Na ions? Dbvr7 vsrs8 :x c8zq0(l =    nm

  Common salt, NaCl, has a dir , j fenknt/lka3+1d*jew5-ensity 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 b5f prh08ryi39 ofm,a1i) .taj ljw. qdensity is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chloride crystal is y5 o/2 t2hjn9 wewhfy)a good insulator. [Hint: Consider the5yw/ewhh)n 9o2 ty 2jf shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombai/sje*7/lq7z co. k h asm7:duly8y9erded with light of slowly increased frequency, begins to conduct when the wavelength of light is 640 nm. Estimate the size of the energy gsi8y/c97lq kmeoe/7j* slah .uyz:d 7ap $ E_g $. $ E_g $ =    eV

  Calculate the longestkzo2n.tm7 3a h-wavelength photon that can cause an electron 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 valence and conducgbu17)bk/et gtion bands in germanium is 0.72 eV. What range of wavelengths can a photon have to excite b) g egu7tkb/1an 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 ar;th0x/pd x+ sl 22vclie $ 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 silicz,x 3u 7df60vuyxtcixa8m wl**y0v-kw b w2x -on semiconductor is doped with phosphorus so that one siliconcatw dm-u7l* xbf3v8kx -0 i,xzv*0ww6x2yu y atom in $ 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_{doping}}{N_{Si}} = $    $ \times 10^6$

  At what wavelength wiy0hytdvr1a6s0hqsq34/zbp i(*02qtojn w 3 cll an LED radiate if made from a material with an energy gay30rq0 y2qbtt(10 q/hov paij6nhz *34dw css p $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits lightdz0sa n2 l;0df of wavelength $ \lambda = 650\ \text{nm} $, what is the energy gap (in eV) between valence and conduction bands? $e_g$ =    eV

  A silicon diode, whose currehxf-- q6k,s md(smuv5 nt-voltage characteristics are given in (Fig. Below), is connected in series with a -u(qvmmxkd,5 fs 6hs-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 (Fiqhl2na 7v 3 ,bqv45qdcg. 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 curtv 9.lp: 5cggxrent, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estimate very roughly t(6;2 alzcr gothe average current in the outputtz2lr6(;ca o g resistor $ 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 significbuejbf56 bw3fsd.hg/ f8 -a-l ant current only if the forward-bias voltage exce 38-lgbu.j h -/6fas5effbdbweds about 0.6 V. Make a rough estimate of the average current in 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 rectif7j*ulh) 3 cwyug/vk;gied with a full-wave rectifier (Fig. Below), whegy)w/g3ulv huck* j ;7re $ 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 base k cnv ( d*z5w.qakxn ;9/1djbwcurrent $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energy of the.mdy- ecpyrm 9wer9 5q4vvzd 0q3 h2gcy0y(2 p $ \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 atom byvs3ozy, 2 pe9rg qg- f2:zb-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 ions is about 0.27 nm. 3 )ygm:t y7e3fpgml s mz7m,q3
(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 bou4 8l/.xh5bh s v4sqjamnd cubic lattice, with each atom connected to six neighbors, each bond havibs q h4xmlh5s8/.v 4jang a binding energy 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 enhenx;uwcjl8a u5l4 32ergy of 1.4 eV. When the molecule is disassociated, 1.6 eV of energy is released. Draw a potential energy curve fo2cuwu;h n elax3j8l54r this molecule.

  When EM radiation is incident on diamond, it is found that light b sn5dbpe01d7j ,tltn4,l k2bwith wavelengths shorter than 226 nm will cause7 2tlkdb5jbbls n ,0n4t pde,1 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 IR light. If the detector on -l 4lz2ha ffh5d4d-3sl1 rv: pqiq ,*sbax6eh the TV set is not to react to visible light, coua5hhpz2 fhsl eaxb d il--3,v l:qd*r44 1sfq6ld it make use of silicon 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 semiconductor2,wq lnz0 .fg,ypho q8, assume that the "extra" electzwof2lq, 80gny qp h.,ron moves in a Bohr orbit about the 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 than 1000 nm. For a solau:is kac:3.w mr cell to absorb all this, what energy gap ought the material i c m3ksaw.:u:have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiati0 k-nh(eny l-jon that can be absorbed is 1.92 mm. What is the energy gap in this semiconductoh(n-0n -kej lyr? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs were fizg7-zo1ojnn3a2 yfxqgdq1 34j x h-,zrst developed. Approximately what energy gaps would you expect to find in green (5,x1 ojzgj1q gf q4nn2x-zz da hy-37o325 nm) and in blue (465 nm) LEDs?
the green $E_g$ =    eV
the blue $E_g$ =    eV

  A zener diode voltage regulator is shown idfw:mmb5g;mi2 dh 2uv f -w71fn (Fig. Below). Suppose that $ 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$