What type of bond would you expec36h)dxv-em 9xdodd: mic-jpa + o-p a0t for
(a) the $N_2$ molecule,
(b) the HCl molecule,
(c) Fe atoms in a solid?

Describe how the molecu mcu37s2* *(ummpwwjv 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 molecul p, h(mw ..,+z.u zlggnf e idkvg6h0qw2g*6uye $ \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 in ugond* udjh+3z 3lz 3)1iv/6nujfo :gto four categories. What are they?

  Would you expect the mol589jzfwg f)wqn51undecule $ \text{H}_2^+ $ to be stable? If so, where would the single electron spend most of its time?{yes|no}

Explain why the carbon akk/pxl:: mc1 nwln(je*i :rc:n0 f.es tom ($ Z=6 $) usually forms four bonds with hydrogen-like atoms.

If conduction electrons are free to roam abou j )waj6y-v6unh)bb5p25k sqct in a metal, why don't they leave the metal entir5) njv 2wcsqby5 a-u 6k)j6hpbely?

Explain why the resistivity of metals incr; nead8rp6o7s c );sureases with temperature whereas the resistivity of semierdc67) 8ups;na;ro sconductors may decrease with increasing temperature.

(Fig. Below) shows a "bridge-ty q 7f)n4k(a4/.j g vh+bunbxeppe" full-wave rectifier. Explain how the current is rectified and how current flows during each half4(u7g) bh an .bke4jxq+pf /nv cycle.

Compare the resistance of a pn junction diode connected in forward bias tnrvqveqwd/ay7k h,z5m) :4 t1o its resistance when connected indv nh/q,va w1t)r5:yqm4z7 ke reverse bias.

Explain how a transistor co 5fli9lwdd8bh:c/u4 zl. nvcih6q p,4 uld be used as a switch.

What is the main differ+fx,qj sb nt7es p;khwjm3wv*/2 r0(rence between n-type and p-type semiconductors?

Describe how a pnp transistor can operate ra.*gyof91a v as an amplifier.

In a transistor, the base-emitter junction and the base-collector junct 9t xkzkp1o,f8ion are essentially diodes. Are these junctions reverse-biased or forwar 8kt,fz po9k1xd-biased in the application shown in (Fig. Below)?

A transistor can amplify an electronic signal, meaning i n()+vdl6r7x/if6lcxmobl l r58vq:m t can increase the power of an input signal. Where does it getv6m : c5+6orqbdvlli7(x l xrl)mn/8f the energy to increase the power?

A silicon semiconductor is doped with phosphorus. Will +mw:elf 8b1d h,.fxxethese atoms be donors or acceptors? What type of semico.+feh,d1m xbfe:lx8w nductor will this be?

  Do diodes and transistors obey Ohm’s law? Explain. -8bdkvliw*y0 {yes|no}

  Can a diode be used tox7 d-ysjtqyhr0xhx* g -y5(k3 amplify a signal? Explain. {yes|no}

  Estimate the binding energy of a KCl molecule by c +*ysjzt lvmm(3lf7*ialculating the electrostatic potential ev3i (j7 tlf*z+ ym*lsmnergy 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 ofdgft8:3-xf j xeoe9 l7 KCl is 4.43 eV. From the result of Problem 1, estimate the contributij l8gx-fd9xetf:e o 73on to 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 thsxo8 mzzo uu6kujx2 t9e4,8q2e $ \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 experimenta y1f1bg6q4wyba *mi2mlly in kcal per mole, and then the binding energy in eV per molecule is calculated from thabbm1am61 iw*y2f4g q yt 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 statemfnhwvs bb) 4 (xtvx3c wb 8dc1*c7i90s in the formation of 09bh xc*d3cx4(w vicm)7bw tvs81nf bthe $ \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 f(ml qhkxp1/ircd te9 (w(- q6$ \frac{\hbar^2}{2I} $ has units of energy.

  The so-called “characteristic rotational e 4;pqll7z gs/d.g2v;dg)xjgmnergy,” $ \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 characterist2xhnh q;:h fiaxqiswrvk30*j /:/sqnx; :vw8ic 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 ( ui:hc8jo6n 3 kjwp3aof 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 molecule given that three successivi9om7h,;i jpu e wavelengths for rotational transitions are 23.1 mm, 11.6,u7m j ph;oii9 mm, and 7.71 mm. $r = $    $\times 10^{-10}\ \text{m}$

  (a) Use the curve of (Fig. Below) to estimate the stiffnessbb8h.)hb ik3+2zmn.ev+y n ro 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 crystd j3 u v44bxgbe24wvntr0 s:b-al is 0.24 nm. What is the spacing between two nearest neighbor Na ions? D = v4 gxe:-n24bbr ud0tw3bv sj4   nm

  Common salt, NaCl, has rmz)/d7sget*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 -:-8,l 0 1htcg,y rm ()ijvwrcagoxtodensity is $ 1.99\ \text{g/cm}^3 $. $s$ =    nm

Explain on the basis of energy bands why the s6 hp,+lmvtp) wz:t sr4-teb) iodium chloride crystal is a good insulator. 4l:tet 6 shm)p -i)v,bz+tpw r[Hint: Consider the shells of $ \text{Na}^+ $ and $ \text{Cl}^- $ ions.]

  A semiconductor, bombarded with light of slowly increased f8/w a(fix/ysv, kgk+rrequency, begins to conduct when the wavelength of light is 640 nm. Estimate the size fyvw(ks/a/ 8g x k,+riof the energy gap $ E_g $. $ E_g $ =    eV

  Calculate the longest-wavelength photon foli/ffi;gv,kkl* k tu/9/ f ,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 cog zeu23/o78fnzm p )uynduction bands in germanium is 0.72 eV. What range of wavelengths can a photon have to excite an electron from the top of the valence band into the condgy7ou e3n/mf8 uz)p2zuction 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 viovc 5,75)mm y7ardb$ 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 phojmrml;ck8zm1 l0:. eosphorus so that one silicon atom iljk1eocmmlz 0rm . :8;n $ 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 a 9z4-p rfgmc(an LED radiate if made from a material with an energy gap 4-mfpga9 ( rcz$ E_g = 1.4\ \text{eV} $? $\lambda $ =    $\mu m$

  If an LED emits light o0/mb5pi.s f jou4ikbf,k)5k f04e ulw f wavelength $ \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 givccaxiufi2.u;c+gt ( * en in (Fig. Below), is connected in series with a batteryu*uc2(aci .ix;+gtfc 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:.sqdx+ (qi wv 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 func;cn4cl:edb 7tzdr7 ,i tion of current, for $ V > 0 $, for the diode shown in(Fig. Below).

  An ac voltage of 120 V rms is to be rectified. Estiqbi0 j)bdx l:1mate very roughly the average curreixb0:lqjb ) d1nt 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 fo4n+fhy;j(x 8+/ edqitw (g pfzrward-bias voltage exceeds about 0.6 V. Make a rough estimate of th pt4fngej;wd /hzqxi+y(+( f 8e 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 with a a,6nthb;) zzu (yz/w4t/eu6 xfp1dmkfull-wave rectifier (Fig. Below),z/kf m,t(1 x;4nt pedyzba6uz6u h)w/ 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 tgz:174)d na hb.m lpgvhe 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 thevle - -savp05s $ \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 translation+3k/fg 1z+ r(ho r tc+ix0eqnial kinetic 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 separation distance between ions is ab +pih qd73hlepzw5,y*out 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 cubi,+ 6zdt7r4 /) cq eurket*uvkxc lattice, with each atom connected to six neighbors, etu+)ckd*ert7 u z/ek6rq,4v xach 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. Whe:rkpmc )/i6 h4mof6 tnn the molecule is disassociated, 1.6 eV of energy is released. Draw a potential energy curve for this molec/mf h ominkp6t :4r)6cule.

  When EM radiation is incident on diamond, it is found tha 5 u5ndb,xn) *qct/cdwt light with wavelengths shorter than 226 nm will cause the diamond to conduct. What is the energy /w*c x5dqtdncn5,) bugap 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 is not to reabno g v ew ghoe84 a++eq2/(a:*hkwxd,ct to visible light, could it make use of silicon a2 wd(w v+ahg oqoe/ e+8*:nbx,4gkhe 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 4:5)zm e*to e d2faygpsilicon semiconductor, assume that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron inyea e:4d*omf pzt)g 25 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 short* )g0vubqve)e )wt1d12 oer uaer than 1000 nm. For a solar cell to absorb all this, what energy gap ought the mat))qea10 o rugvuvwee) 1db2*terial have? $E_g$ =    eV

  For a certain semiconductor, the lop/j mf -ef3/zf1 9+y p9v)oexn( 9eok:dwiypo ngest wavelength radiation that can be absorbed is 1.92 mm. What is the ener nee+zpp pym fwfeod v/9:1fy(/x oi)93 9k-jogy gap in this semiconductor? $E_g$ =    $ \times 10^{-4}\ \text{eV}$

  Green and blue LEDs became available many years after red LEDs were fi. 1mk(yt)b svhrst developed. Apprtv s(1b)mh.ky oximately what 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 regulr/xc+ + vx:jovuu x.v(9uf/x0an i )pjator is shown 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?    $\ \text{k}\Omega \leq R_{\text{load}} < \infty$