What type of bond would you expect for qw5kkc 66.ap .mj 105l6raxi my1 wqoi
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecule d (p* rzozs7(na jc9q,$ \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 gmm5z;*xb sa41 m r9ef$ \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 ,o k rfjwlr57-categories. What are they?

  Would you expect the moleculesemddlb ha8s0h8h n d,he.(qz 5-)x1u $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon atom (a mq6- g .soq9or:x3if$ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in a met :r9 bwrxbf9d.al, why don't they leave fd.x9:rb rwb9 the metal entirely?

Explain why the resistivity of metals increases with temperature whemlh c8d(gc* -ureas the resistivity of semiconductors may decreascdu8cgm- *(h le with increasing temperature.

(Fig. Below) shows a "bridge-tya0 ) wkwk(9klr gu;n*upe" full-wave rectifier. Explain how the current iwkka9r0u ln (k;w*g)u s rectified and how current flows during each half cycle.

Compare the resistance of a pn junction diode connected in forward bias to itd8o:ys *o8 xp s/pd3yts resistao8ddpxy s*o/ys8 3tp:nce when connected in reverse bias.

Explain how a transistor co ylw66:s:8dzuhz,t yfz0 (bb uuld be used as a switch.

What is the main difference between n-type and p c1+e7w9nuta22h gvlg-type semiconductors?

Describe how a pnp transistor c;jqo9 ;26bqj+l ux r.fbbt,qnan operate as an amplifier.

In a transistor, the base-emitter junction and the base-collector juncti a zwx,ac35t., 6s,zzptr4mhnon are essentially diodes. Are these junctions reverse-biased or forward-biased in the application shown ip3acwnm ,,xtzz st ,h6raz.54 n (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can increase tuhpn, 285 mhpbhe power of an input signal. Wheb5p 8u hhnpm2,re does it get the energy to increase the power?

A silicon semiconductor is dope;;is4ali * yb,do tabla.: u)jd with phosphorus. Will these atoms be donors or acceptoa sbu l:iily; ;aa 4b.t*o),djrs? What type of semiconductor will this be?

  Do diodes and transistors obey Ohm’s law? Explc3 g9o gb*89mqlea(nk* b1lbtain. {yes|no}

  Can a diode be used to amplify a signal? Eh qw-r8ve-wa7xplain. {yes|no}

  Estimate the binding energy of a y-s 5jzh61jk;asjzgg.x7) oy KCl molecule by calculating the electrostatic potential energy when t 67jh1zxg zs;sa- j.y)k jo5yghe $ \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 eneuj7a+-kjez2p:we +fy ;/0g pz7i rx mdrgy of KCl is 4.43 eV. From the result of Problem 1, estimate the contribution to the zw+y jee+2z idf a;77pump/k:g-jr0xbinding energy of the repelling electron clouds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energy of t-p cy:j (an1czhe $ \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 ofte8dha38/roo - edgpw8n5ju j z/n measured experimentally in kcal per mole, and then the binding energy in eV per molecule is calculated from that result. What is the conversion factor in going from kcal per mole to eV per molecu 5on g8ue/ 8jjd3/zp8arwd-ohle? 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 eu4z :4yr8bw nthat in the text for the states in the formation of th4y8:e ubrz w4ne $ \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 quanti-)nd.b678i yan le gmgty $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotati ihgygy9l2ooyfc6ai((l +**1idyar 4onal 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 characteristicqnboox59 9 dx(q; h4gu rotational 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 atom4xkn,sesp 7j y/l4h t.s 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 NaCl molecule given that g mebv q4c e5 ;9mlpseea6(:7cthree successive wavelengths for rotational transitions are 23.1 mm, 11.6 mm, and5sq b(69apvcmme c; 7l:ee4ge 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) to estimate td-dv s yi2e re*:zux:2he 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 “nearx minktwi 3e:kr; ii w8h*oj4zd: 80u6 kh50uyest neighbor” Na and Cl ions in a NaCl crystal is 0.24 nm. What is the spacing between tw n*ewohi4mj0 w8d83t5hkz xiukir :06 kuyi;:o nearest neighbor Na ions? D =    nm

  Common salt, NaCl, hasg8 g:vvoyhg7g9vhj 6/uw3m ge-yg ; -b a density 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 densitmdo;f s-1 k ewuz)h:6xy is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chloride crystal is a goo6/ vckq.gsw n;f9fz4ld insulator. [Hint: Consider the 4q9 vlnszfk;6/ g.cwf shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombay5s4tu ,dlsb 2rded with light of slowly increased frequency, begins to conduct when the wavelength of l4su52yst,d bl ight is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelequ- d9kgil(m8 ngth 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 conduction bands 2qoqstk41lm atx,n s7j.x43uin germanium is 0.72 eV. What range of .o7mst3 n,jtsu44xl1qxq2a k wavelengths 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 ark+8vb. olym zp2l c51l.r yir3e $ 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 semi0xmenr4zx p-*88ptd td)0 p mwconductor is doped with phosphorus so that one silicon 8)xnr 40eppd8*dtxtm0w zpm-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 will an LED radiate if made from a material with an energy;( uok xifsfax; t*t26 gaf;t *(usi6x; ta 2fkoxp $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wavelength t,; 9vidj+sp3ewa4 u:am bcb6 $ \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 characteristics are given in ( uhtz:q+pu1 fo7/l 7vbw,*n+b+by xtcFig. Below), is connected in seric,n u++p* whybl/ ubo7v:17ttqfb +xz es with 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 (Fig. Below) is coyfr /a p6;yi-djf22zyx-qw e9 nnected 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 curreo,*j9h4xec zg-c e)f qvw+ns /nt, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be .-tn oqukr:lerc 5j*8 rectified. Estimate very roughly the average current in the output resisto.:urlj r qnc*t8-o 5ker $ 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 onl(a)teq5;dbs r1+v4 avfxg 5c hy if the forward-bias voltage exceeds about 0.6 V. Make a rough estimate of the average current in the output resih5r aa() +1x;v4 5b vcsetfqdgstor $ 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 voltam/t jn5,+d-p,2ywtujehvm *i6)qwr yge is to be rectified with a full-wave rectifier (Fig. Below), *+),jy6,/5phrdmnutqtm i-jvwy ew2 where $ 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 basp31 uz1 w1bugupf*jhn r7a( (se current $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energy owe.wr /4o9dqa f the $ \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 kineticx mxq11l2k4s9e.o qoh energy of an atom 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 separatio-c dj * 0vvlf/x1fcv;xn distance between ions 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 1tvvw: 7k.9 xglo. isebound cubic lattice, with each atom connected to six neighbors, each bond havinsw g17ktv.:v oxe.il 9g 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 (7wxtkz)w;diwv.5gca u 4p b*to have an activation energy of 1.4 eV. When the molecule is 57w(pwca bx;uvwtdg.4iz ) k* disassociated, 1.6 eV of energy is released. Draw a potential energy curve for this molecule.

  When EM radiation is incident on diamond, it is found that lit m,b;r5o.2 0c vdd1elx ifxp+ght with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the energy gap+1v.dom0r5;2tx dpbex,i cfl between the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emits IR light. If thm(y)3d -qwuw 3flzswe/u r+q. e detector on the TV set is not to react to visiblrqquefsw-(33 dmz l+ u./ww)ye light, could 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 2cjk/ te c 1tk(ut1:yxatom in a doped silicon semiconductor, assume that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the grouxt/(kcyt:2 ejuct 11knd 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 fw) lhjms4c/j-zod15 nm. For a solar cemh/ 4l)dfz-wo c1jjs5ll to absorb all this, what energy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiatiyf e ha ht/ma*0.-2pdion that can be absorbed is 1.92 mm. What is the energy gap in this shha-0 fmdt 2aepy/ i*.emiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs bg o*9qkw9fq(cbe4e ,fecame available many years after red LEDs were first developed. Approximately whatf kboqcq9( f,e*weg 49 energy gaps would you expect to find in green (525 nm) and in blue (465 nm) LEDs?
the green $E_g$ =    eV
the blue $E_g$ =    eV

  A zener diode voltage regulator is shown in (Fig. Below). dda5n1ev v2(d o+,rzfvfb*7 gSuppose 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$