What type of bond would ufvyb;qt6 k8 is4gd04 you expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecu rhru v yz:2o.s 2zk::q*:ffjt6; mgmzle $ \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 moleculeq 3cu ejc+j;k- $ \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 a- dy(hdccb;s b.p2bo/re they?

  Would you expect the mua40mkm8pmof akw 3/-eo)zl8 olecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carb/h-e4(d7vg cyw 8q(3 zguo-* ayohbgdon atom ($ 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 leave ogu8 iqk ,je4:the metal ene4qg,o:j kiu8tirely?

Explain why the resistivity of metals increases with teyn8r5rchyd81 s n-(emmperature whereas the resistivity of semiconductors may hye5 nmy(r d18crn8s-decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Explain how the curreuzyq+z9lbe e+zl 06 h7nt is ry0z7+q6e9 elzh+l bz uectified and how current flows during each half cycle.

Compare the resistance of a pn junction diode c:pck3jt99 jbm5ef5zh2c3slhs t ;c x2onnected in forward bias to its resistance when con53 h :z k9c e5xjf2;lps9b2c tcjhst3mnected in reverse bias.

Explain how a transistor could be usqs5 l7zn5) fi )mrpdw5ed as a switch.

What is the main difference bet foye1c/8: jgl3a9w h -wn7zcj ddfo::ween n-type and p-type semiconductors?

Describe how a pnp transistor can operate n cq560,t-6azy-)vysupnov 6-ye lugas an amplifier.

In a transistor, the basehz2on;wn2;:q5dp txp -emitter junction and the base-collector junction are essentially diodes. Are theseox2;pp:w2 n5 hqtdn;z junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it can increaz 4d w(frzpd:;k0)fbkse the power of an input signal. Wher)z:0bp kf fw;dkr (4dze does it get the energy to increase the power?

A silicon semiconduct31sdkwqstu5; fpf)2e.t 9 cm lor is doped with phosphorus. Will these atoms be donors or acceptors? What type of semiconductor will tt1uk ;ls5sf 923tc fdqpm e.w)his be?

  Do diodes and transistors obey Ohm’s law?ofn1ly bpo2- 6 Explain. {yes|no}

  Can a diode be used to uzh+v+ 1 sw3xsamplify a signal? Explain. {yes|no}

  Estimate the binding energy of a KCl mol6 rl 3v;afow4me9 u0tkecule by calculating the electrostatic poteu;4 e0vktlwf39rm 6oantial energy 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 mq-w kx yvw.7,2wvsv+4.43 eV. From the result of Problem 1, estimate the contribution to the binding energy of the repelling electron clouds at the equil7wqmv.2ww-ksxvv,y + ibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding eneks qhhyr(*p asinpy )800n)8c.mia3k rgy 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 p ujd: q tz*ir)ptfpk:ktv:26w; a*e l+er mole, and then the binding energy in eV per molecule is calc+k*tt qjt epv ;z2a*kip: )d6lfwr u::ulated from that result. What is the 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 similar to that in the text for the states inmg wd(x 190 p5fq1hsin the formation of thg xq9s1ni f1hwpm (5d0e $ \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 quantityier+cc:6k+ d.;qak s e/kp4gi $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotay f6fair.d:.3ai ky4u tional 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 rotationaom5hjl lp( :/wl 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 thei-8c pscn69irj gpx bhhg;u(w.t374b $ \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 thedee;0,n*wwc p NaCl molecule given that three successive wavelengt;0we*ewnd cp,hs for rotational transitions 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 constant xdv -ue;n0)9rzatibco 8:8qw $ 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 crysvn*;bv5 kf(gd zrt0/ttal is 0.24 nm. What is the spacing betw/vvkz;5g0ttr *f nb( deen two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a density o8ek t zdn31v7af $ 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;e 6qnmic11 dl whose density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chlouhy-1-zsv 7 vbride crystal is a good insulator. [Hint: Consider the shells of zv1 vyu-bh7s-$ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased frequen7 +6yeh27klj ck(m uxhcy, begins to conduct2hh+67l(ck7eu jmkyx when the wavelength of light is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon that can cause an electron in silicon wmo u)e) :dm6 gq11hjt($ 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 germanium is 0.72 eV. .u8o h;yhxf w6 m2*ouyWhat range of wav.8yy* oxw6uofh;m2huelengths 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 aryn(nsifgt-r6 twc53fr,p. b /e $ 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 semicondu gb4w70hw8kflctor is doped with phosphorus so that one silicon atomwklg4 80h7fbw 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 radial1 iwg-bu -9u *2v -iy)jjrekote if made from a material with an energy ga uj-)oe-219i gwkluv byrj *-ip $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of nmhqb()c u i uvh42f9pv)d09rwavelength $ \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 (Figz7pu 80mmj 9xz. Below), is c7mjx zzum p098onnected 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 co-9hu x da9a6fsnnected 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 cuufu.f(v 6otsd*tmd5;zh 0gpvp/ s.7j rrent, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. d8.s; qw d7i6l. pvtxb+qvyai t0nz90Estimate very roughly the average current inq ;b8dz.l0 w+ti9i.p7q6s y0 xvnta dv 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 c wo.eme-;5 w 1lryodux5-/ qdeurrent only if the forward-bias voltage exceeds about 0.6 V. Make a rough estimate of the ao. de1/w;mel5 dwo-uqyxe5 - rverage 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 rectified with a full-wave rectifier (Fig. Be qg15)i8 u1pcnl at:bf0ws(3tmiqyok- o(r ;k a(g:q;liwn uroi5 k )1-stbk(t0m y38 pco1qflow), 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 base cdbnbrgyabt) x,dik+n3owm 4 mbz+d1 n:q4-9.urrent $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energy oil:+ib i9/vcrs h76pkku 5sq2f 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 energy of an atom or molecuuofh r0yunbdr6 wg56 .s(mf((le 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 distanceh;.*r;gf3 2 n czapo2ruq *rqe 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 bound cubic lattice, with eac;nol e -h(gzi5m(klr 9h atom con5(olzl ( ; ehi9-kmgrnnected to six neighbors, each bond having 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 energy of 1.p,a 5 6kygbyc.zy *sh,cl ve4q*s-5to 4 eV. When the molecule is disassociated, 1.6 eV of energy is rel .,apvsy4,5oq6zg5 ey c *kbt h*yc-sleased. Draw a potential energy curve for this molecule.

  When EM radiation is incident on diamond, it is found thaz ;;whau b iyjtg835a m(vhh3y9v/o2 wt light with wavelengths shorter than 226 nm will cause the diabzvvhth; y (y g2ha59 /3uawj38im;womond 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 lx-xw.- kjw/rcight. If the detector on the TV set is not to react to visible light, could it make use of silicon as a "window" with .x/r kj-wxcw-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, assume 50npq(v h k3ubt:x-xgthat the "extra" electron moves in a Bohr orbit about the arsenxhn p 3:0(ubgk -qv5txic 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 j;6 4r8ck6jgd s7c8jk kz3ndp. For a solar cell to absorb all tspck gzjd8d84kj3cn7rj; 6 6 khis, what energy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longest wavelength radiation that can be absorb -hs;weykeh yvy-.w ;in/ae14; col.med iay..eliyew-1-vew;; ; hshyncmo4 /ks 1.92 mm. What is the energy gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs bqr)ovdh30fa d8x+qq4 gij. x 7ecame available many years after red LEDs were first developed. Approximately what energy gaps would you expec g.i 784d+o0xxf vdrjqq a3qh)t 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 (vxt a1 +f m/y*q6kb,buFig. 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$