What type of bond would you expeck8dx1s1bseus a1a 1,qw. o,*xpgf+c jt for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecuc v567ejakhq6 - l d2aktpn+b;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 molecule eb8k7gon6x 0czj (hx;$ \text{H}_3 $ is not stable, the ion $ \text{H}_3^+ $ is. Explain, using the Pauli exclusion principle.

The energy of a molecule o7qg)kqv -cl2can be divided into four categories. What are they?

  Would you expect the;bxxr/ 1uvn*i molecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbkbfplj ,2nr 0qi7u5:ps5d45 nu wtx u0on 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:pq gxdq*k+-w24t kk v the metal ent qw*+4k2k tkxqpd:-gvirely?

Explain why the resistivity of metals increases with te 6 943 jnau-pu1,ihpkwpd8/g rorck f,mperature whereas the resistivg 4 1/3p,irrcaj68u-u9wfnho k, pkpdity of semiconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-type" full-wave rectifier. Expla;oel2h ew.. 7gx/aufdqbo0- lin how the current is rectified and how current flows during each half a.hbgolx-2we 7uq l f/;e .o0dcycle.

Compare the resistance of a pn jund*vgph+g s5nis75bq7/ vf a+oction diode connected in forward bias to its resistance wiq +g/ savnosvgp*d7b5 7h+f5hen connected in reverse bias.

Explain how a transistor could be used as awk0vx r3l;vp8v , uu5v switch.

What is the main difference between n-type ;5a q7 xj nured+8z74eni: 1jix7l khwand p-type semiconductors?

Describe how a pnp transistor cai+l2z u8* die+xlyn4 i0fhw/ise i 6n,n operate as an amplifier.

In a transistor, the base-emitter junction and the base-collector junctiv9( m,ro: 8dpd7p3axa e*fws0laiti ;on are essentially diodes. Are these junctions reverse-biased or7imeo(i p tvl3aa ;d80 9xswf*,:arpd forward-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning it6e82yulocu on oxn7h; ;cj5 7w can increase the power y nj8oe5ho26 7co7uxn;w;ulcof an input signal. Where does it get the energy to increase the power?

A silicon semiconductor is doped with pa rx)35xyg+ -edim:d84 aejads 1: qzihosphorus. Will these atoms be donors or ac)4q imga15+edes ri- a8:d:xxjyz a3dceptors? What type of semiconductor will this be?

  Do diodes and transistortg f :miw0o5-t5p-v x,d6 alfvs obey Ohm’s law? Explain. {yes|no}

  Can a diode be used to amplify a signal? Expl2q(dc c:g+z yw 9ajsi.ain. {yes|no}

  Estimate the binding energy of a KCl mol sptgzig99k :k udej+ (/y, qu*wgj2a,ecule by calculating the electrostatic potential ener:9 gjgqi*dgwujyku ( ke/2+,t a,s9zp gy 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 result of Problem 193stp y+j6rr d, estimate the contribution t+t96jpy r3drso 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 tnxo4). 3b 6upkw)he3ca/zod x he $ \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 exptmnh,7axcvin 7 iv**p.x i,4pf9aic3 erimentally in kcal per mole, and then the binding energy inp,.nphic,x*3 i9fcmv t4x*7aiv7 i a n 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 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 text25qvm iu bd9(v for the states in the formation of themvvdiu2(b5q 9 $ \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 jmewe,s l0)5 th;6-w5annv ob$ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotationaprf9k0f-u3w)e x 9n zgl 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 rotateqw-/u+ux ;. ixja 5goional 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 inz;w1kadjq9b rwnq5h d )*,wx/ 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 ;bl/*dui4kgs7pz.y:oe rrg* that three successive wavelengths for rotational transitions are 23.1 mm, 11.6 mm, a*db:ieo zr s7*lkp/r 4g;yu.gnd 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Belo :tm47s3h8 tgim5l odiw) 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 ions in a NaCl crystal iv4+tl3xoceq- 0( y3cs3q vid2.x dtj ms 0.24 nm. What is the spacing oitx cj3 vc3e(d x03t4d2-yls .qq+ mvbetween two nearest neighbor Na ions? D =    nm

  Common salt, NaCl, hz ssd 4k;n00c*p topc;as a density 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 whose densitn;qiy go.0o2w y is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the sodiuc 0qxpt/d;t0am chloride crystal is a good insulator. [Hint: Consider thet;dcxt/ap0 0 q shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased frequency, begins to 4jd f)3 iax6boconductx6bo)3iad f4j 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 siliconusvj5 b9p+k,ci m+clw/,(q .;jds olw ($ 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 conductio7isn:q*n,0mitm4 ghs n bands in germanium is 0.72 eV. What range of wavelengths can a pho:ihmt,7 qs0ning s4*m ton 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/+y cz7065xt/aqlv pzgw,vu c $ 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 phosphoruy)hdg5*a00x z0ohtjegjj7 8j s so that one silicon ajdjheth g7z *0ao j050gyj8x)tom 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_{doping}}{N_{Si}} = $    $ \times 10^6$

  At what wavelength will an LED radiate if mad y6hxqn xz67 c6bpa;k2e from a material with an energy gax6k2 p7cn6z; ayxqh 6bp $ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light of wa00l2i2monyqte) f ) eavelength $ \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 characteris ;4vli+c+nbg stics are given in (Fig. Below), is connected in series with avi+cslbn g4+; battery and a $ 960-\Omega $ resistor. What battery voltage is needed to produce a 12-mA current? $V_{\text{battery}}$=    V

  Suppose that the diodeo9.;fdw iem6 /u,hb 1p-duz by of (Fig. Below) is connected 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 curren/sasvfqoy f5x * c9 eg2ty qeg89tkc,cb,l2;(t, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estjo8wu sq ; pzoy8z+j;(imate very roughly the average co jpwj+zy88zq;(s ;uourrent 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-biasbu+*sark o1s+ voltage exceeds about 0.6 V. Make a rough estimate of s1ku+os+bar* 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 rectified ryqrw7 mf6ik2.z 5eps:oa8n1 with a full-wave rectifier (Fig. Below), wh:knr ef1m6ai2ro57zp8sq. y w ere $ 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 ae1g:v y5xpxmz4 wpg* 6n 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 of the raw,r.qs tb;,15edok $ \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 ene mccbe16 l u b:p51awdzg)v11olx8o0 hrgy 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 dista:9n qy h9ar3punce 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 bo.3mzu,b rnzo 306zny- tb9+fvbeo0owund cubic lattice, with each atom connected to six neighbors, eacob zye360 uz3rn+ fob0bm -wvn,z9.to h 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 dz9+(x az64e5jlwav r have an activation energy of 1.4 eV. When the molecule is disassociated, 1.6 eV of energy is released. Draw a potr9zd w6el4ja5+v(xzaential energy curve for this molecule.

  When EM radiation is incident on diamond, it is found co w;9j2-o6igcvqzd-sd.xe + that light with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the energy gap between the valenc;v 92o g-w qjixcodzesd.+ -c6e band and the conduction band for diamond? $E_g$ =    eV

  A TV remote control emits IR light. I: .a,-jbf)d5o wa 0e*nrdpcrhf the detector on the TV set is not to react to visible light, could it make use of silicon as a "wind*0 a5-hdrwec,.rjfn o dp):ba ow" 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 silwcw xd/n u2-o.0 jnh3jynv(3f icon semiconductor, assume that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the ground state, take into account the dieleu(fj0 23 3.c/nyno wvhjdx-wnctric 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. F46w1 jqv qhd9nor a solar cell to absorb all this, what energy gap ought the mat 9n1 d64whvjqqerial have? $E_g$ =    eV

  For a certain semiconductor, 0ay y c-r,y li6+,ovydthe longest wavelength radiation that can be absorbed is 1.92 mm. What is the energy gap in this s-vc+,y,y0idr6 yoa lyemiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red Lmip ia72f2qtdk;8s c5 EDs were first developed. Approximately what energy gaps would you expect to find in greei7m 8fp id2ca qt5;ks2n (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).f9*p vy ulz:zso6g);v 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$