What type of bond would yolcuuydjg8ke.q/z5c m( ,t;t8-kl j 8 bu expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molwdv,ow,3 tm0p l5a/vp,pr jbrj9 +lu5ecule $ \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 ffbw8/s- d :9dz9o fnr$ \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 categorcrv; b zj;hz6q2z;o2/do6f6*b goqp sies. What are they?

  Would you expect the molecule t jx2+o 67mnazquq.:i $ \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 fm(orgt)a * ,2r jpd*-j)bezl ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in a metal, whyh :7fklggkp :o, qgq6* don't they leave th,:l qgg 6fg7q*ph:o kke metal entirely?

Explain why the resist qjl.l(a z.z igz o489hkmcb96os /-h cehr;,vivity of metals increases with temperature whereas the resistivity of semicon,vqh/o.h9cko-z(c.z 4mlz s h9;jlar 86 i gbeductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain how zpty9 /t3 t(9hwfo+,ns; cnz b7b9e mkthe current i +p/nbc zk yh o;t,( 9fs9wt39m7tznebs rectified and how current flows during each half cycle.

Compare the resistance of a pn junction dimg rsu*0cm *(lpov9k :ode connected in forward bias to its resistance when connected in rever*s0pg*ol9mc(m: urvkse bias.

Explain how a transistor c s iy fun2*8gw/t-z3vi. wgix1ould be used as a switch.

What is the main difference between n-type and p-type sem -lo,ure6vv0*,cziy miconductors?

Describe how a pnp transistor can operate as an amjl8 .kl7k wucv;i)pv0plifier.

In a transistor, the base-emitter junction and the base-collector jun1wbavz8 c64enction are essentially diodes. Are these junctions reverse-biased or forward-biased iac8n1ezv4wb 6n the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can incre25o2 xtposkvd1u-1 k) jzlqeq; 2 u j-lc))ebdase the power of an input signal. Where -1 zkps2 q;l ))devj1bcd 2xjq5)2lu-eo oktudoes it get the energy to increase the power?

A silicon semiconductor is doped with phosphorusagvssy 7bcq1hf5 p:j 1n ;)./vadxr3k6 at r(h. Will these atoms be donors or acceptors? What type of semiconductor will this b;a j7) :fxqd1hn r/v5hst3syka (pg6cb a.1vr e?

  Do diodes and transistors obey Ohm’s law? Expb .dw*3 gcwc2glain. {yes|no}

  Can a diode be used tocx8qafst8 .14()yj y lle)9xzzb k4gg amplify a signal? Explain. {yes|no}

  Estimate the binding energy of a KCl molecule by calculating the electrosz4qw-q b4vgbw 9qn 8d4tatic potential energn4b984zbgqwqv4w d- qy 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 KCpdmk)j6qkfd 33p9 leb/6 uq+al is 4.43 eV. From the result of Problem 1, estimate the contribution to the binding energy of the repelling elect9 lqd pfb6/ekmu 3q6jkd) p3a+ron clouds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energy of thc,qir +t(f* 8 hiqk)aae $ \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 w+p le2+mm qs,v r*f2fexperimentally in kcal per mole, and then the binding energy in eV per molecule is calculated from that result. What is t2 e*m2 l+,p rwsvmqff+he conversion factor in going 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 simi/n dl wgc: c4;wp gg(vsdmwa*u83 bc+(lar to that in the text for the states in the formation of the s+awg /p n(d4gb;: cd wg uccm8wlv3(*$ \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 quantity xqvv3pv s 87:uo 5stn+ygz.q-$ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotationaluprjpyxg :y0r+0g1 ,w 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 character/o-xi*2q2w ky 9po0jy a*usm ia*1e eristic 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 a f:b5,s clvtn8i961sm l +amrltoms 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 mqh)u(fpglf 4- jo18rr;- xoz NaCl molecule given that three successive wavelengths for rotational transitions are 23.1(zp1uolgfrfh- qjx 8- 4m o;r) mm, 11.6 mm, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) to estimate the stiffness constant fyxjqy .3)z3h $ 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 “nry:a3 2e;da:h g+gv miearest neighbor” Na and Cl ions in a NaCl crystal is 0.24 nm.e :ryav :mg32i+ gdah; What is the spacing between two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a density of d3 zpj s8z b8/a:u92akm9fpr7hw+bcw $ 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 dhjf+tl1 iw4 lm+voxl;b)hd; lt be;21 ensity is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chlorid/ ; 3)8oyc ,dszbzslyse crystal is a good insulator. [Hint: Conssd ;co3y,b8sy)z ls/zider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with lqxnm gqx2r59j1vw+ w2 ight of slowly increased frequency, begins to conduct when the wavelength ofwm9g25x +v2r qj wx1nq light is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon that can cauoxb u9n tszr28a. le/ jweb-40se 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 in germaniun vvb2d6uwe l 4w6e)6xm is 0.72 eV. What range of wavelengths can a photon have to excite an elec nxvwbd vw)466e26eultron 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/nbh)gqm :, gw) 7uqw8 uz7aone $ 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 with phosphorus so that one8 z1l1;em ri0hsop;zj silicon atomr18izs e1ozlmp h0j;; 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 wi e/kxm w -3mm-nr52mqvth an energy gap-wm q-n /rmx v3k2em5m $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light ofro hpqo;6(mb / wavelength $ \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.qx:r0iss-4b v/vj*r 9j,x szpkwg p 3 characteristics are given in (Fig. Below), is cks4xvrjsbsj 3/ wqg ri:z px v.,*p0-9onnected in series 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 connected in gakc9+uvij)w4 b +ci2 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 ff 9qzspl+53os 4xmw m.w3dny ;unction of current, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estimate very roughly the ave3vuhed(ny* e7) lh a2rrage current in the outpu h )7h*v23rye ud(elant 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 significv4y vq bg ;z0itg*/af5ant current only if the forward-bias voltage exceeds about 0.6 V. Make a rti /g;vfv* g y045qzbaough 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 beoysck ym 6 cfcj: (i0/tmd/48:zcq7ay rectified with a full-wave rectifier (Fig. Below), wherjcoy4s :cm(:q /8m /6kc 0yz 7fyadicte $ 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 be0oy:kt75fijk -)x x zctween the base current $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energy of tn0hc)t+ ry sd2he $ \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 enerujg)/2rb(j9df :t)p motq9 zegy 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 separation distance between ions is about 2s*bd vwl/1ym 9y+hob0.27 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 cubic lattice, with ea6xlbwv(jzl0i :c( 1nq ch atom connected to six neighbors, each bond having a binding : l1jb (6xz(nw ivc0qlenergy 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 ac,a 3opyzo 7 u86p,yvrltivation energy of 1.4 eV. When the mo puro3,zvy8 ply7,o a6lecule is disassociated, 1.6 eV of energy is released. Draw a potential energy curve for this molecule.

  When EM radiation is cq dsnv+0 n jd8al;p,,incident on diamond, it is found that light with wavelengths shorter than 226 nm will cause the diamond to conductn 8cjap0; s,nv,dd +ql. 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. yh c;u4f jd53xbg:l1fy1 nx*o If the detector on the TV set is not to react to visible light, coudy ;bhfco 3 y1xug 4jf*x:1l5nld 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 semicondmv9y 22:ye/ehhqipeu rb0p)*uctor, assume that the "extra" electron moves in a Bohr orbipumh 2h:e0py*/bqiyr 9e v2e)t 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 wavelengthsjt9aq. a5 9top shorter than 1000 nm. For a solar cell to absort aao5t p.9j9qb all this, what energy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelengtde;bj5st9qt0 rs5 cm4 h radiation that can be absorbed is 1.9cr 0sb;tq49d tm5e 5sj2 mm. What is the energy gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many yeaq+s(elyi 20g grs after red LEDs were first developed. Approximately what energy gaps would you expect to find in green (5ie+sy( 0g2lq g25 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). Suppose that w7 ca*e6i v,rx auj-2fkg4r5h $ 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$