What type of bond would you g y80 y do drom)ft09dxj7lz;,expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecu9rersd,:*+3g7 tsf snt +tmiw le $ \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 molecul9 wnkk9;l9ga2:q9q zi 4ql dtqe $ \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 are4c/5zdf w9q m)r vf1fg they?

  Would you expect the moleculee s/u (31xskskd;w 0ld $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon atomd98n61 wuhe s8a kf6y1arv4ma ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in a metal, why don't they lea:h2 x-rwy lqx hw(ep,0ve the metal enxepr 2h(w:yw hl 0,qx-tirely?

Explain why the resistivity of metals increases with temperature where m8 szlrav6 8).)b:.uuqreb/qryr;fx as the resistivity of semiconductors may deczqrmb)ealv . r y b:;rxuq8fu.s r/86)rease with increasing temperature.

(Fig. Below) shows a "bridge-typx7)oe wq+m 0j*(+1w2ey4av lkwa kwpx e" full-wave rectifier. Explain how the current is rectified and how current flows during epx2jv7wmxwq kw ka+e 4)yla( w+0e1 *oach half cycle.

Compare the resistance of a pn junction diodksxl jc/p47u,us48h me connected in forward bias to its resiss/c8,7p h uluxmkjs44 tance when connected in reverse bias.

Explain how a transistor could be u;j*lf k)w wwq6j;kud(n7mai 2u67px6mb*d wx sed as a switch.

What is the main differb xqps e;d5 hgv)u6)v2ence between n-type and p-type semiconductors?

Describe how a pnp trans ct oj 2+)n)0hhbc2z9doir-ydistor can operate as an amplifier.

In a transistor, the base-emitter junction and the base-collector junction 3 par9 etod(geqz74 ;8xnen* oare essentially diodes. Are these junctions reverse-biased or fore pn8 dox e*t3(q7enz gr;94aoward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it c2ynlu;vefw3+m: f.s 3zwn h*jan increase the power of an input signal. Where does it gete; ulnv f*. wmjf: z3+2ys3nhw the energy to increase the power?

A silicon semiconductor is doped with pkgvuiq u8)zyq4.6gd58g 2ti l hosphorus. Will these atoms be donors or acceptors? What type of semiconductor wil2ii 4dy58q.lgk) z guqu8vgt6l this be?

  Do diodes and transist(35ee0l ezy qd*tb5czors obey Ohm’s law? Explain. {yes|no}

  Can a diode be used to 6h r;/i5k,uc ochr) sqamplify a signal? Explain. {yes|no}

  Estimate the binding energy of a KCl molecule by calculating the electrostati;5bx9 4 s5jq uimev4rac potential enq9si 454exrba5j u;mvergy 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 4.43 eV. : uq; vk1s msq0 1otry)53immvFrom the result of Problem 1, estimate the contribution to the binding energy of the repelling electron clouds at3uvs5 r:t;mmq1 1)qo0k syimv the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energy of the e k7m5bnch-2rex /luj3xl+k :$ \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 ofteh wz 6ad9djl(wa-l)tc0 l-l9bn 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 molecule? W(hl6ad9d)-wa jwb0lc z9t- ll hat 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 in the. +avq(8 (jovbj)r 5uuopz f+u formation o v5++u(f vurzo 8pjoa)qjub.(f 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 quantity -2+ xovczmw;a $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characterist6kgp1 c8o+6 coerryk3ic 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 characteris(s,:tl xwnp2- zta*kftic 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 atoms in2fbdx3: a9u0f(s kuc t 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 three successive wave) *frx 3f8 k0v9 dgil3poen1jelengths for rotational transitions are 23.1 mm, 11.6 mmrx k 08iegne*vjp)f3of ld1 93, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Be0u7bzmbf2 zw4 low) to 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 iihas7uz x/ 3e4q8 ) u*vul2kqoons in a NaCl crystal is 0.24 nm. What is the spacing between two nearest neighbor Na ions? D =kq)8l */ z2ouausq4hu3e7xvi    nm

  Common salt, NaCl, has a densitr 4tj;ev,eo,)sb ym8j y 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 K41zp:gmcmol u 3 lb+9dCl whose density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis or darb71q-ujk8/q *km f energy bands why the sodium chloride crystal is a good insulator. [Hinjkqru*bqa7m-8k /d r 1t: Consider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light,bm1g mbiqo-;be73y 6ves: sl of slowly increased frequency, begins to conduc1bq ms,i lv- 7ebm:ye3s6;bg ot when the wavelength of light is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelengthq 6w zwpy(h/1e 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 im*lac+z8 tyal u1:8lj n germanium is 0.72 eV. What range of wavelengths can a photon have to excituzj1*:lt cyl8l aam+8e 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 arlg c/f0 gwn3i9lvqd :s4)knw1v :dw.oe $ 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 onedem4 v2;c:tg 2dzwi x21fom k- silicof2xidz 2m g -v4kw td1cm2;e:on 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_{\text{doping}}}{N_{\ce{Si}}} = $    $ \times 10^6$

  At what wavelength will an LED radiate if made from a mate 8wethrg*l sxlo o(faj:t +325rial with an energy gap xj3o2+tl*( glohate85w rfs : $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wn0 g* zi5mvj0zavelength $ \lambda = 650\ \text{nm} $, what is the energy gap (in eV) between valence and conduction bands? $e_g$ =    eV

  A silicon diode, whose current-vmo-pi 9v9aq6 ,.z jlw4v9rqrzoltage characteristics are given in (Fig. Below), is connected in series with a battery am prvwi6zlv-94zrq .99,aqojnd 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 seriesp8qlga5ip. obg 886a+u34q ys zg9 xbj 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 functipn-lvv( xsrc-q:d (2q on of current, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estimate verjx( a 8 5;mgzep6qza9lc *hfw dw37it4y roughly the average currm8cd7* ( jh3fe ;xawz5tg96iwzq4pl aent in the output 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 the 9tt+(lwz049n kukr b5vs bcv0 forward-bias voltage exceeds about 0.6 V. Make al09t bv bvku9k4n5+(sz ct0wr 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 rj6u4lql( ,9e zoy-6s nxcffd 4ectified with a full-wave rectifier (Fig. Below), whelj,l4y(sf6f6-d 9qxze ou4ncre $ 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 ancmwpcfgt z1(6t,5-vr cy 3 +xm equation for 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 oftnn-a,lfu mtq :(s6ey4 l 8m ai(:6ftb 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 kinetic enev,gg 2/bqj -cbrgy 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 :d ( wl.:k: ;/gc9zdidc syvhcions 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 su( yhr(f:)y3/b pfvh wolid with a weakly bound cubic lattice, with each atom connected to six neighbors, each bond having a binding p)bwh 3 f(fv:/u(hryyenergy 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 c moxj-.xd h*1k0) fwxeV. When the molecule is disassociated, 1.6 eV of enex.- o )xc0h1d wkm*xjfrgy is released. Draw a potential energy curve for this molecule.

  When EM radiation is incident on diamond, it is em(ak7 ;wg7nw it/3 zmfound that light with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the energy gap b/zmwaw (ti;en gmk73 7etween the valence band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emw2s7c 9gc-db(x*w: n ;o(2 l z92xerggqoe fbtits IR light. If the detector on the TV set is not to react to visible wc xg; (*gznq (f2b7go9-wtl29cdx: 2e bresolight, 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 atom in a doped silicon semiconductorrqt0er( ;;qajrti9ttpe )d2 9, assume that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take into accdetqr(9itt;qt ;)2raj9 r0epount 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 solar v pxep68f *fm6cell to absorb all this, mfpp 6f6vx*8e what energy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiation that can be absoro:v, qf bw1r,hbed is 1.92 mm. What is the enr,h :wo bqf,1vergy gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs were fir1dmm tg,)e ,fq llu4q p9w+q*gst developed. Approximately what ed m4,)m*e,1+qlqgl9gpf uq tw nergy 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 (Fp+-igxlfn* kpzt r)62ig. 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$