What type of bond would youfwaf ej9.);8/kypfbq expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molect4hml -fiv muctiu 7d18k1 ;c5ule $ \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 t- +/lp+m8rl)sxx km7yf:ejt $ \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 divi.mh4ta2a:ua;1bsc7 bcs8 me o ded into four categories. What are they?

  Would you expect the mole 4pffu17l *vlu-op1w kcule $ \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 (cvh je;lm)2c8 nd q86o$ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in a metal, w(o+ hph,u- g: aivrq2uhy don't they leave the mer+( 2hui,q -av:uog phtal entirely?

Explain why the resistivity of metals increases with temperature w2obd38frn)vr5qgo5 ide5v ,5rf.jey b 0q5vv hereas the resistivity of semiconductors may decrease with increas2f i5 r5r 3d vro85do)qyqjvgebfbv.en55 0, ving temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explaix8 .zfixr/ f1zn how the current is rectified and how current ff /18xzzrf.ix lows during each half cycle.

Compare the resistance of a pn junction diode co6nlmigd9qq7 4nnected in forward bias to its resistance when connected ln 46mq9igdq7 in reverse bias.

Explain how a transistor could be used as a 6tjp fnm4a ; vk(32g.8yc+b1cij atvjswitch.

What is the main difference between n-type and p-type semicoo*7ln9yx;i l znductors?

Describe how a pnp transistor can operate as an avj2v4fd g a.* 2(lqsdumplifier.

In a transistor, the base-emitter junction and the base-collector j1olwl;se+ va; unction are essentially diole ;also;v1 +wdes. Are these junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can 70e sphqgzm q6nu; unl6-jly:-hi 9 c(increase the power of an input signal. Where does it get the energy to increase the power-u y0zqujsn h:6-q l(l9p h6g;cmn ei7?

A silicon semiconductor is doped with phosphorus. Will these atoms 6rv1b,.z;ai ebz4)vl7x-cyrvu+ vvybe donors or accepto-v+br)ex,v.uzrly; vy4b1v7a6z v cirs? What type of semiconductor will this be?

  Do diodes and transistors obey Ohm’s law? Ee3 1grdr +d2mgxplain. {yes|no}

  Can a diode be used to amplifyq q.9pwq:: bx15gytm r a signal? Explain. {yes|no}

  Estimate the binding en4* flej-/ff 6rpw *qxzergy of a KCl molecule by calculating the electrostatic potential energy when xz4/ j*fflqr-fep*6 w 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 tp( 7wnw gvj)g5 l,qg2 c(nf2sehe result of Problem 1, estimate the cong 2jwg27(wsf 5 p(e qc)vgln,ntribution to the binding 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 thhpfopsa-2vh e7;t: - 6 c5wcpwe $ \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 tv(ppl .k gk,d cai,nr+37fk2l hen the binding energy in eV per molecule is calculated from that result. What is the conversion factor in going from kcavp(r k,k.cild3kf2 ,a 7ngpl+l 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 in1ecmr v/zp 1*l the formation of th*v1pec / 1zrlme $ \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 quantiyujta031 5v5 8n nl2gamale2dty $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characw-i8 oaba*hpucog+9 2 teristic 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 charpmal8o xj(; )o1p(bjb : q3rpoacteristic 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 separati*aub z 9 py hxorag;3/0.1mqawx0 3 ,jn*bdqngon 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 NaC5-aceu 6uvjq (yi2 lki5t9+v ml molecule given that three successive wavelengths for rotational transitioni- vi+qe9 6(tvu 5myl5aj2cuks are 23.1 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 cy-zq ac6c.wu8 onstant $ 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” m403bznw,u :mb s7p esNa and Cl ions in a NaCl crystal is 0.24 nm. What is the spacing between two 7:n, mu pzbswe3m0 4sbnearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a xwbf(n0g 7k3rdensity 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 whoseo9as0hj -o l6pt69 m)opzsw/ w density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chlor p6tv,t,y1c)m iynwc-yqa- 5xide crystal is a good insulato5piy 6c1t w- taxqn),cm yyv,-r. [Hint: Consider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded wi(; y358kyu a zqtk7shoth light of slowly increased frequency, begins to conduct when the wavelength of light is 640 nm. Estimate the size of the eneru73;yz 8ks y(otha5 kqgy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon that can cause an electron in silicos(1(+ow aa6ifoyf6v t v. oqi)n ($ E_g = 1.14\ \text{eV} $) to jump from the valence band to the conduction band. $\lambda $ =    $\mu m$

  The energy gap between valen3/ 5s g dbtb2dfxgbl-+ix-d8tce and conduction bands in germanium is 0.72 eV. What range of wavelengths can a photon have to excite an electron from the top of the valen fx/3gbd+gtx-dtb-5ibl2 8 sdce 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 ares0ws.9n 3 eckk4npr +v $ 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 one sgr; xpeyj r)f)neiu:/n/8we 3ilicon a3r/pew n f8i: yu e/rxej);)gntom 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_{\text{doping}}}{N_{\ce{Si}}} = $    $ \times 10^6$

  At what wavelength will an LED radiate if made fro.mv1kg)rg9m2 fbpa (q m a material with an energy gapbkq )rgv 2f1gamp(m.9 $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wav4 ,kencwsdju9b04:tuelength $ \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 (Fig. Below)9z1gmur/m: nr8t)no9 p /cn gs, is connected in series w /nu9 rp9n8n1m )grgsczto :m/ith 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 conne nn)m .a 8:a2d+mmpp51o-vplecqq2zhcted 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 fun2, )s9bb5 zkuisk5t5f5 4g q mj2zvhxgction 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 rk/tw 3w3pxfa2*zzvo :oughly the average current in the outw 3*f/px 3o:zwt2 vakzput 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 significant current only if t2csh or/nw6qnz 3a) i1he forward-bias voltage exceeds about 0.6 V. Make a rough e)1z/rnahsc6iq o 2w 3nstimate 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 rep70.+uww**ba-n cajbwn *nc pctified with a full-wave rectifier (Fig. Below), where wc- *ba+w*ncua njwpn p 0*.7b$ 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 for1 0lljart1uw7 the relationship between 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 tzrq l6wm.i 7z,he $ \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 or molecule is about xv ws7ait hwpgp3,9 )*v4v qk-$ 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. cs94(-zyabc.kezgi) e f.wq627 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 solidbgbz2yd u7a47c4l0 md with a weakly bound cubic lattice, with each atom connected to six neighbors, each bond having a bindi7acdb42 m47gd 0uy lbzng 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 zc*usk e66wn -0dxyh(energy of 1.4 eV. When the molecukd-xhsne 0 *z(6cyw6 ule is 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 t,5o. :mjp cfrkhat light with wavelengths shorter than 226 nm will cause the diamond to conduct. :pjr.5 fkmoc, 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 the TV set is n j3r29ra5t/lmox-x w not to react to visible light, could it make use of slx5 ro9an32xt -mw /jrilicon 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, assum ohs+6w p3z-am.p5fgtdn;4jze,exr +e that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take into account the dielectric constanwg3; md zrp-.nfeo4a x 65ejz++st,hpt $ 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 shorte-jg,qn4e )akzs15f5 c kgo* ror than 1000 nm. For a solar cell to absorb all this, what en, r-z5 jskek4q gcgo1n 5af*)oergy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiation that cbxe*zl s72r7eh/- ddcan be absorbed is 1.92 mm. What is tdr 7*7 sx/e 2ec-zdhblhe energy gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs were first+h vrwfs gz e7z*.g9jzd8o.(t developed. Approximately ww zo s he9gzgd t*.+jzf78v(r.hat 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). Suppose y 2rpn th9b66tkekf50that $ 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$