What type of bond would *+f )ftq5 evqjsr, (4rxea:gmyou expect for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the mole4q7y ux5ruv5 lwws),gs5i- ljcule $ \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 z,un7 +1xhx em$ \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 ab92+x *lovhs3pd 1 zjfre they?

  Would you expect the mo4wjb 1q3 :z:h-iwpq)gsuypqx0x8r v/lecule $ \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 (u+oidw0bh;8 73ttow a$ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free * ttq,j)4 y9tdn7zqlu to roam about in a metal, why don't they leave the metal entirey,7tl9nu j ztqt qd*4)ly?

Explain why the resistivity of metals increases with temperature whevx :gwtyccyu ,(b1 hn( 0ipg);reas the resistivity of semiconductors may decreas;p g: tnb y1yxu(iv0ghcw, ()ce with increasing temperature.

(Fig. Below) shows a*kvljj*, w73 nings6 b "bridge-type" full-wave rectifier. Explain how the current is vnj3nlw**s g ,k67 jbirectified and how current flows during each half cycle.

Compare the resistance of a pn juno 0 iuyp65 zxqlw*g0wn)2*g,cbu/ ilnction diode connected in forward bias to its resistance when connected /xw02g5n ,y upiulliq*g6coz)w*0bnin reverse bias.

Explain how a transistor could be (psh:pxx fks e, g-)z64 brnm4used as a switch.

What is the main differegi2q s gs+v5y *p,uzm2nce between n-type and p-type semiconductors?

Describe how a pnp tranhif i50 f8/q. ipdd3sysistor can operate as an amplifier.

In a transistor, the base-emitter junction and the base-collector junctid5ui-k oc:j: ion are essentially diodes. Are thesekiio : :c5uj-d junctions reverse-biased or forward-biased in the application shown in (Fig. Below)?

A transistor can ampli5y2k+kmp aolqo4 id 3)fy an electronic signal, meaning it can increase the power of and lmo qi)ay2534ko+k p input signal. Where does it get the energy to increase the power?

A silicon semiconductor is doped with phosphorus. Will th1uwuop5ju.v) ese atoms be donors or accep) v 1uuwjo.5putors? What type of semiconductor will this be?

  Do diodes and transistors obey Ohm’s law? Explaxy 7 :vgwxd *tghl0(a4in. {yes|no}

  Can a diode be used to amplify a signal? Explainn1 2ztz-nmobv9 ,e br1. {yes|no}

  Estimate the binding energy of a KCl mojpkm-qwa: 6: olecule by calculating the electrostatic potential energy when th6owmkjp:-q a:e $ \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 result of Problem crpwsvg868 wt2 *t3 pknt(j/p 1, estimate the contribution to the binding energy of the repelling electron clourcsppw*t pnw/ 8t3 j2v68gk(tds at the equilibrium distance $ r_0 = 0.28\ \text{nm} $. $PE_{\text{clouds}} =$    $\ \text{eV}$

  Estimate the binding energjso:0t:0 5/m d0vvy zc--gwegwq fl d7y 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 of8vg2 zl cub0c,ten 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 ,ugl2cz bcv 80per 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 qvcargb 34 4r9r) r7iy hzsot10b8 n1vthe text for the states in the formation of traq4 vrz8s73yc1nbrog0 491) brivh 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 quantityh *r6j5 ie 52nk 53 aul3g4ivyahbri8b $ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rota0dgsp8 - evarxk4*-iitional 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 rotational en) lsz3owr/g9huf x )jhp f,n76,x xec7ergy, $ \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 separaoyvc1k5o *l s uiu:910rt *hgjtion 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 NaCl mopdn i1(wk.dad*c.yf py7+ 6rf lecule given that three successive wavelengths for rotat(d7wc+ f6nd r ya1 .kp.pifdy*ional 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 stv0uj /08hld ixgop97 jiffness 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” N4*uljl )kr0rl + 51gete/tzrqa and Cl ions in a NaCl crystal is 0.24 nm. What is the spacing between two nearest neighbor Na ions? qlz0rrgt4rk 5utll 1e/e*+ )j D =    nm

  Common salt, NaCl, has a dens osponra( ;bz;2p1f5v;5 pvymity 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 o 9oz35jqlan45z6ju (5fo9 ap rj 4ngiKCl whose density is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodium chloride crystal is a gooemv sxmx -s 0e 3rf1j 4qdo9d9z3:5ivvd insulator. [Hint: Consider therm s vz-104ivm d95ose 3fexq jxd9v:3 shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased frptuj;pzg*pdt9p s a2(xseg8g;. ruiv;* . vg:equency, begins to conduct wh.ztj.gpg2pse9gtu p;8*druxg*i v :vs ;(p ;aen the wavelength of light is 640 nm. Estimate the size of the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength ph f/,ybj9a f(y;oi39sm. qvkctoton 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 ban8crhqo h9q:3ducy m1d m/x; (vds in germanium is 0.72 eV. What rangecxq93m/rd hdo cqv;uy :8h(1 m 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 *q3 pqbfw:(ea oo 9x-t zkmhjyc4g;lfb1 u14:$ 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 ik9g (8pvv2 lxys doped with phosphorus so that one silicon atom i 9gkvp(2xl8y vn $ 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 fr-ya 2 7h;n(ih8ejg 1mmn e.twjom a material with an energy gapjnejny h1;8 ti a- hw2e7mgm.( $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wavelengtw 2wrtf ;71dqyo4*oc nh $ \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 chara(aw,;okilf ) acteristics are given in (Fig. Below), is connected in series with a aflkiw o( ;)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 seri w7/b53;ujo9ntc(rsowr z)x zes 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 7 lbr 0p,7pqsk:lvo5efunction of current, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectif /t(kwucq* -+ bks1sceied. Estimate very roughly the average currcqku es w1-(c s+*t/bkent 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 forward-biasp4zc b,7sd cg/ voltage exceeds aboup/b4cdcg 7 z,st 0.6 V. Make a 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 re5*lkutwn0 rv8: c xv +kiun+ jz8wvm0*ctified with a full-wave rectifier (Fig. Below), wherztcu+vvnv +8wimwl: 80 *jkx05ru nk*e $ 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 c /6(zcd weux( p7m+frrurrent $ I_B $, the collector current $ I_C $, and the emitter current $ I_E $ (not labeled in the figure).

  Estimate the binding energy( j:xan;(tfxc of 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 hm kmp1(;3w, ,ts( a,ixosh fckinetic energy 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 sepaxk 7l98kt:ogx ration 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 weakly bound cubic lattice, with each atom i w qn6m8ph+kao fvut:81w)y0 connected to six neighbors, each bond having a binding energ+h 8q0o8pw: ay um1fni6 vtwk)y 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 enerd6, asj ot*,k:h sdmggpn+-v*,. nndegy of 1.4 eV. When the molecule is disassociated, 1.6 eV of energy is released. Draw a potential energy curve for this molecule.,6og :-dd,smj+* ehvnn*gatn . pds,k

  When EM radiation is incident on diamond, it is found that light with p (wx3 h2us6rgewdn(883bn pa,dy hx)wavelengths shortersbxw (hu8 and8 hdn26pe 3gwx3(y)pr, than 226 nm will cause 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 se9m blznr(vy9oyv .- 7*ba8ro st is not to react to visible light, co7bavovrm(* 9 y noz.yl-8b9sr uld 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 silicr jtsivo: 9:t /* 9:yhca6kbfp):nwgeon semiconductor, assume that the "extra" electrono6s w9ijn /b:r*::tch9fet:gvkyp )a moves in a Bohr orbit 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 wavelengths shor2q)r.h1mg iyajy22u if q0jo4a+ 0kubter than 1000 nm. For a solar cell to absorb all this, what energy gap ought tgj i.ji1 4qk+my 2bao2)quf0arh20uyhe material have? $E_g$ =    eV

  For a certain semiconducto5 r5-( /ccfin7 uw.e*znxbr2 wz.utirr, the longest wavelength radiation that can be absorbed is 1.92 mm. What is the energy gap in this u7i*5rwr.bfu nx/2zc5zn w (ei.r-tc semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs werbp/(qzychj7 m- en4m*e first developed. Approximately wqj y( *nc b7/p4mm-zhehat 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 sh -yb7qq hmtv 6x(xe9v:own in (Fig. 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$