What type of bond would you ex:ljv/iyb-dd3 pect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molec; 9 v:qgwno-p 5xhso/ ,akwf-gule $ \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 molecul9xd h3sv54 kzq9lcfy j9 xc*m-e $ \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 divideob(py5r 9s 9yd( t(glnryzp t,5d:,ke d into four categories. What are they?

  Would you expect the molecule x c.mq(rax v4i ixf6b/kk- 09k$ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon oy(su(nvs n*1atom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam about in a metcgy es*sa4 y r5ud gyuyv;54--al, why don't they leave the metal entirely? u;ayyd-5*4s s -4g5ueg rvyyc

Explain why the resistivity oxom ujh;r:(ho 0v )qi1f metals increases with temperature whereas the resis ;jxr) 1h 0miovh(:oqutivity of semiconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-op. 1to0 qf/iywave rectifier. Explain how the current is rectio/1oi ypqt0 f.fied and how current flows during each half cycle.

Compare the resistance of a pn junction diode connected in forwar(tl9ze4b()tjoazq 7m5v nw 5c d bias to its resistancez5 b5nzql( v(ecot4j )9ta7mw when connected in reverse bias.

Explain how a transisb3.pi :7we6pla8c7el 5wa 0br5rsjz dtor could be used as a switch.

What is the main difb*,dzp 8eotrevf )y- .4da9ksference between n-type and p-type semiconductors?

Describe how a pnp transistor can operate as an amplifier.t*hjh10r enl o22l jl v1xh)2ob/-isg

In a transistor, the base-dl u7xv;s1/mud7;ni aemitter junction and the base-collector junction are essentially diodes. Are these junctions revvlns7 ad1mu7dixu/; ;erse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronicv0, al.okqh,h:2 h: ku8aqydl signal, meaning it can increase the power of an input signal. Where does it get a8h02lu akh,,dq:v :oy.q khlthe energy to increase the power?

A silicon semiconductor is doped with phosphorus. Will thew7 kcun+fo;k.jo9m6 b7fi z2pse atoms be donors or acceptors? What type o.9uo6kinc7fkf +bjp;m2 ow 7zf semiconductor will this be?

  Do diodes and transistors obey Ohm’s qg1mupb/udpksq y;p*6+ dgkp i .k*44law? Explain. {yes|no}

  Can a diode be used to amplify a signal? Explain. {yes|no r/.h ag:1 bprj-d5jlw}

  Estimate the binding energy of a KCl molecule by caljhf7 )n j5.qnbculating the electrostatic potentia n7)qj.hb5jnfl 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 4.43 eV. From the resultr, 0rcs:etmw9 kpb5 8h of Problem 1, estimate the contribution to the binding energy of the repelling electron clouds at the equilibr trp5s:98hkbmer w0,c ium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energ 9:op80hx lokjy 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 per mo8wo4hit(. h 5 fa/jvbquyjx56le, 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? What is tvoy(wqb 5jj5h68 / ah4tfuxi.he 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 formationgnu6pl6oa-4 d of ta gl6p o6dnu4-he $ \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)3cml2y gs+qbkr+ x9v $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotational energy,”zv) tae;qewij36 0 k*u $ \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 chakmcgokb*22 5dracteristic 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 in the 0 6qm.7xdih,)n awai a$ \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 three71jwukf0ut793kc xb60qg lr z successive wavelengths for rotational transitions are 23c91 773q0jb kuu lxz0fwtk gr6.1 mm, 11.6 mm, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) to estimate the stiffne;zerl5 e 7)2ohk cka.bss 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 ions in a NaCl crystal is 0.24 ,;nkt;sp9 efkjt75 q6 hk ;fvnnm. What is the spacing hs,jeffn;; 6n9t; pt57kkk vqbetween two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, has a os+ i)ik13uo8v 9lndgdensity 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 KCc,6i u m.srw/2isli7 bl whose density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bap3:qycrt 5h3y kwoh43nds why the sodium chloride crystal is a good insulator. [Hint: Consider th4 h5o3 r3pc qkwy:hyt3e shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased frequency, b5b1a+s: usbllg 0r4w lal91piegins to conduct when the wavelength of light is 640 9u 4as5rlwsb1:p ll+gib1l a0nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon that can cause an electroticxj8 z5;7vn i2fb3sn 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 vale2kyt t d/ytj;g99;a dsnce and conduction bands in germanium is 0.72 eV. What rangk2t g t/d;9jya s;dy9te of 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 are sn;1d1w,:na2o vafs l $ 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 tacanf2k0;g v;cc1 /ykfze 6n4hat one silicon atom i;c4 yn126kcfcav;/nea gf k0zn $ 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 materi) 58ettbm 3oaxi muh::; dtf1fal with an energy gapti8dtm15 fbo3atf:u;e :)hm x $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wav t5 kxv*9lzz66hljmqn;q6i3kelength $ \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 charact3y2oc kn) uo:ai x fwh*6nmm*0eristics are given in (Fig. Below), is connected in serunam:wfomxo**yk 6) c032nh iies 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) oj0t*ncnquk5 bv 8j1nnected 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 cu x asfxn dzp-y(4ck0u80ubz3;rrent, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estimate7lt z46 u1pdsp very roughly the average currentp741ptz s dlu6 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 pass e6*a nr;tz7ybxbt* p2es significant current only if the forward-bias voltage exceeds about 0.6 V. Make a rough estimate of the average;arbe6 xp 7tn**zb y2t 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 fu:(e- ugsqi mx0ll-wave rectifier (Fig. Below), ws:eq -0( igxumhere $ 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 t t 3ip g*q(0fat8.dci u*r7fsbhe 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 thm;w,jd( ,einu e $ \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 molecz 6q8vgw +yeq.m7u9g5srx g6zule 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 separatiovlko:2s or9 x8n 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 weafy(v srd+9jwzr*9har 41 f9bakly bound cubic lattice, with each atom connectes f9raab +d94v9jz 1r(yr*w fhd 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 1.4 eV. When zfe4 bs/gg99mukm1 9j7k it3athe molecule is disassociated, 1.6 eV of energy is released. Draw a potential energy cum97ubkeggk aijzt9s4193 fm/ rve for this molecule.

  When EM radiation is incident on diamond, it is found tha 9 f6m1kwslj4ot light with wavelengths shorter than 226 nm will ca s 1kmjlf9o64wuse the diamond 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 light. If the detector on the TV set 9ff/byz,k.*nnn0otp is not to react to visible light, could it make use of silicon as a "windo* 0nf.bp/o, kn tyfzn9w" 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 silht8o .ce 3(gbpicon semiconductor, assume that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take ib ctohe.p38g(nto 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.t3t+g,j xu6s w For a solar cellxjw,+stu6 t3 g to absorb all this, what energy gap ought the material have? $E_g$ =    eV

  For a certain semiconductor, the longesti66, ek i abw:d/qk8lz wavelength radiation that can be absorbed is 1.92 mm. What is the energy gap in this semiconduc:a zdwb86, ki6eqikl/tor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many yeo/hjdo5)by5e- xfp7 oars after red LEDs were first developed. Approximately what energy gaps would yo5/ hd 7f jo)yoxe-b5pou 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. lbjt ;la2s7w5s9 m6gfBelow). 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$