7-Hạt Nhân Nguyên Tử

7/26/2019 7-Ht Nhn Nguyn T

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LUYN THI I HC VT L 2014 Thy Lm Phong

Gieo hnh vi gt thi quen. Gieo thi quen gt tnh cch. Gieo tnh cch gt s phn. ( Dick Lyles) 1

TNG HP CC CNG THC C BN V CNG THC GII NHANHVT L 12 - LUYN THI I HC 2014

CHNG VII: HT NHN NGUYN T (8cu)

Bi 1: S Lc V Thuyt Tng i Hp Ca Einstein.Hn ch ca c hc c in v s ra ca thuyt tng i.

C hc c in ( hay cn gi l c hc Newton (1642 - 1727)),thi gian xy ra mt hin tng, kch thc v khi lng ca vt uc tr s nh nhau trong mi h quy chiu, d vt c ng yn haychuyn ng.

Khi nghin cu cc vt chuyn ng vi tc xp x tc nh sng th c hc c in khng cn ng na. Einstein xy dngthuyt tng i chung cho tt c cc lnh vc v Vt L:

Thuyt tng i hp( gi tt l thuyt tng i, ra i vo nm 1905): ch nghin cucc h quy chiu qun tnh. ( l phn chng ta s tp trung tm hiu)

Thuyt tng i rng: nghin cu cc h quy chiu khng qun tnh v trng hp dn.

Cc tin ca Einstein: Tin 1: Cc nh lut Vt L u c cng mt dng nh nhau trong mi h quy chiu qun tnh. Tin 2: Tc nh sng trong chn khng lun bng c = 3.108 m/s trong mi h quy chiu qun

tnh, khng ph thuc vo phng truyn v vn tc ca ngun sng hay my thu.H qu:

S co ca di: L = L o 1 -v2c2

(trong L l chiu di khi chuyn ng, L ol chiu di khi

ng yn)(Nng Cao)S chm ca ng h thi gian: ng h gn vi quan st vin chuyn ng chy chm hn ng

hn ng h gn vi quan st vin ng yn t = t

o

1 -v2c2

(trong t l thi gian khi ng yn, t ol thi

gian chuyn ng). (Nng Cao)H thc Einstein gia nng lng v khi lng: E = mc2

Khi lng tng i tnh: m =m o

1 -v2c2

( m ol khi lng ngh ng vi khi vt ng yn).

Nng lng tng i tnh: E = mc2 =m oc

2

1 - v

2

c2

theo Einstein, vt c khi lng m th c

nng lng E v ngc li, khi lng vt i mt lng m th nng lng vt cng i mt lng Ev ngc li.

H thc Einstein v nng lng: E tngitnh= E

ngh+ ng nng E = Eo+ W

mc2 = moc

2 +

12

m ov2 W

= E - E

o=m

oc

2

1

1 -v2c2

- 1

ng lng tng i tnh:p = mv =

m o

v

1 -v2c2


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Bi 2: CU TO HT NHN NGUYN T.Cu to ht nhn:

Ht nhn c kch thc rt nh ( 10 -14 m - 10 -15 m) c cu to t

nhng ht nh hn gi l Nuclon. C hai loi Nuclon:

proton (k hiu11H, m

p= 1,0073 u) mang in tch dng.ntron (k hiu 10n, m

n= 1,0087u) khng mang in.

Theo bng tun hon cc nguyn t ha hc ca Mendeleep, th:S proton = s th t Z trong bng tun hon. ( Z gi l s

nguyn t s hay in tch ht nhn c gi tr bng s in tch nguyntch trong ht nhn) Tng s cc Nuclontrong ht nhn gi l s khi(k hiu l A).

Do A = N + Z N = A - Z.K hiu ht nhn lAZX.

Bn knh ca ht nhn: R = 1,2.10-15 A13

(m)

Th tch ca ht nhn: V =43R3 =

43 (1,2.10-15 )3.A (

V htnhnlun t l vi s ht Nuclon)Cng thc tnh s ht:

Tnh theo m: N =m.N A

A (trong m l khi lng ca vt, A l s khi, N l s ht)

Tnh theo V: N =V.N A22,4

(trong V l th tch ca ht nhn tnh theo ktc)

( c bit N A= 6,02.1023 : hng s Avgaro)

ng v nguyn t: l nhng nguyn t m ht nhn cha cng proton Z nhng khc s ntron N.

VD1: Hydro c 3 ng v:11H (proton)2

1H 21D (tri)

31H

31T (triti)

VD2: Carbon c 4 ng v: 116 C,126 C,

136 C,

146 C.

Cc ng v chia lm hai loi: ng v bn v ng v phng x ( khng bn). Trong thin nhinc gn 300 ng v bn v vi ngn ng v phngx t nhin v nhn to.

n v khi lng nguyn t:

n v khi lng nguyn t: l n v u c gi tr bng1

12khi lng nguyn t ca ng v 126 C,

c th: u = 1,66055.10-27 kg; khi lng ca mt Nuclon xp x bng u. ( Ni chung mAA.u)

Theo h thc Einstein E = mc2 chng t khi lng c th o bng MeV/c2 .

Ta c: 1 u = 931,5 MeV/c2Nng lng lin kt ht nhn:

Lc ht nhn:L lc lin kt gia cc nuclon ( lc tng tc mnh)

Khng phi l lc hp dn, lc tnh in.( F G= Gm 1.m

2

r2, F C= K

q 1.q2

r2)

C bn knh R rt ngn tc dng vo khong 10-15 m.

Mun tch Nuclon ra khi ht nhn cn phi tn nng lng thng lc ht nhn.

ht khi:bng hiu s gia tng khi lng nuclon to thnh ht nhn (Mo) vi khi lng M ca ht

nhn.


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k hiu m = M o- M = [Z.mp+ (A - Z)m

n] - m

o

Nng lng lin kt ht nhn:l nng lng ta ra khi cc nuclon ring r lin kt thnh ht nhn v cng l nng lng

cn cung cp pht v ht nhn thnh cc nuclon ring r: W lk= m.c2

nng lng lin kt ringW LKR=W LK

Al nng lng lin kt tnh cho mt nuclon v c trng

cho s bn vng ht nhn. Ht nhn c nng lng lin kt ring cng ln th cng bn vng.

Bi 3: PHN NG HT NHN V NNG LNG CAPHN NG HT NHN.

nh ngha: phn ng ht nhn l cc tng tc gia hai ht nhndnn s bin i chng thnh cc ht khc: A + B C + D. (trong A c xem nh l "n", B l "bia" v C, D l sn phm mi).

c bit, hin tng phng xl trng hp ring ca phn nght nhn: A C + D. (A l ht nhn m, C v D l ht nhn con).

V d:(a).Nm 1909, phn ng ht nhn u tin do Rutherford thc

hin.42He +

147 N

178 O +

11H

(b).Nm 1934, phn ng ht nhn to ng v phng x u tin.42He +

2713Al

3015P +

10n ( Piere - Mari e Curi e)

(c).Phn ng t phn r (phng x):22688 Ra +22286 Rn

Cc nh lut bo ton trong phn ng ht nhn:

Gi s xt phn ng ht nhn sau:A 1Z 1A +

A 2Z 2B

A 3Z 3C +

A 4Z 4D,(A

i, Z

iln l t l s khi v s hiu nguyn t

ca cc ht nhn A, B, C, D, i = 1,4) v mA, mB, m

C, m

D; v

A, v

B, v

c, v

D ln lt l khi lng v vn tc

ca cc ht nhn tng ng. nh lut bo ton s khi (A): A 1 + A

2= A

3+ A

4

nh lut bo ton in tch (Z): Z 1+ Z2= Z

3+ Z

4

nh lut bo ton ng lng (p): m A

vA= m

C

vc + m

D

v

D(B lm "bia" ban u khng c vn tc)

nh lut bo ton nng lng ton phn: E + KA= KC+ K

D

(trong E l nng lng lin kt ca ht nhn (xem bi 2), K l ng nng ca cc ht K = 0,5mv2)

Ch :(a). Trong phn ng ht nhn, KHNG c s bo ton khi lng v ng nng.

(b). Bo ton s khi A Bo ton s Nuclon (A = N + Z)(c). Bo ton A v Z dng cn bng phng trnh phn ng.(d). Bo ton ng lng v nng lng ton phndng gii ton.

(e). Quan h gia ng lng v ng nng l K =1

2mv2,

p = mv .

p2 = m2v

2 = 2m

12mv2

= 2mK p2 = 2mK p = 2mK

Nng lng trong phn ng ht nhn:tng t vi cc d kin trn, ta c t m o= m

A+ m

Bl khi lng ca cc ht trc phn ng, m = m

C+ m

Dl khi lng ca cc ht

sau phn ng.( m o m).

Ta c E = m.c2 l W lkht nhn = W phnnghtnhn v m = m o- m l ht khi lng.Nu xt theo khi lng mth ta c:

m o> m E > 0 phn ng TA nng lng ht SP BN HN ht tng tc.


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m o< m E < 0 phn ng THU nng lng ht SP KM BN HN ht tng tc.Nu xt theo ht khi m th E = [ (m C+ m

D) - ( m

A+ m

B)].c

2

t m Sau= mC+ m

Dv m

trc= m

A+ m

Bln lt l tng ht khi ca cc ht sau v trc PHN

m Sau> m

trcphn ng TA nng lngm Sau< m

trcphn ng THU nng lng ( m

Sau m

trc).

Cc loi phn ng ht nhn: Phn ng kch thch:( c tc nhn bn ngoi) nh nhit hch, phn hch, v.v... (hc cc bi sau)

Phn ng t pht: (do tc nhn bn trong) nh phng x. (hc cc bi sau).

Bi 4: PHNG X - CC LOI TIA PHNG X.nh ngha: phng x l hin tng mt ht nhn khng bn vng t pht phn r, pht ra cc tia

phng x v bin i thnh ht nhn khc.c im:

Qu trnh phn r phng x ch do cc nguyn nhn bn trong gy ra v hon ton khng ph thucvo cc tc ng bn ngoi.

Ngi ta quy c gi ht nhn phng x l HN m, cc ht nhn c to thnh l HN con. Cng nh phn ng nhit hch v phn hch, phng x lphn ng HN ta nng lng.

Cc tia phng x v ccqui tc dch chuyn trong s phng x.

c im Tia (42He) Tia electron - v Tia pozitron

+

Tia gamma (ht photon)

Phngtrnh

phng x

So vi htnhn m

_ Ht nhn con li 2 trong bng h thngtun hon.

_ c s khi nh hn 4n v.

_ Ht nhn con tin 1 bng h thng tunhon.

_ C cng s khi.

_ Ht nhn con li 1 bng h thng tun hon._ C cng s khi.

_ Khng thay i._ Bt c phn ng phngx no cng c th kmtheo tia gamma.

Phn ngminh ha

23892 U

23490 Th +

21093 Bi

- +

21084 Po

137N

+ +

136 C

22688 Ra +

22286 Rn +

Bn cht

_L dng ht nhn

nguyn t heli, chuynng vi tc c2.10

7 m/s.

_L dng ht electron

c vn tc xp x bng c= 3.108 m/s.

_L dng ht electron

dng c vn tc xp xbng c = 3.108 m/s.

_ L bc x in t c

bc sng ngn nht ( 1, th h thng vt hn,phn ng dy chuyn KHNG kim sotc v nng lng ta ra rt ln ( c dng to bom nguyn t).

Vi k = 1, th h thng gi l tihn, phn ng dy chuyn kim sot cvnng lng ta ra l khng i ( c dng s dng trong "l phn ng ht nhn")

Vi k < 1, th h thng gi l di hn, phn ng dy chuyn khng xy ra.

Nhvy, c iu kin k 1 th khi lng nhin liu ca ht nhn phi t ti mt gi tr tithiu gi l khi lng ti hn m o( v d vi

23592 U th khi lng ti hn l 15kg, Pu l 5kg).

L phn ng ht nhn - Nh my in ht nhn:


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yta cn ch mt s vai tr quan trng:Thanh iu khin: thanh Cd (Caimi), Bo dng hp th ntron duy tr h s nhn k = 1.Dung dch nc trong l phn ng ht nhn l D 2O (nc nng) dng to ra ntron chm.Thanh U235 to ra phn ng phn hch nh bit.L phn ng ht nhn c xy dng v bao bc rt kin c trnh r r phng x.Cc sn phm ca phn ng phn hch u gy nhim mi trng, mt s cht phng x gy

bnh cho con ngi ( xem bi 4).

Bi 6: PHN NG NHIT HCH - BOM HIROnh ngha: l phn ng tng hp hai ht nhn nh thnh

mt ht nhn nng.Phng trnhphn ng:

D + D32He +10n + 4 MeV

D + T+ 10n + 17,6 MeVc im:

Tnh trn mt ht nhn th W taraca nhit hch < W

tara

ca phn hch, nhng tnh trn mt n v khi lng th W taraca

nhit hch >>> W taraca phn hch.Nhin liu ca phn ng nhit hch l teri (D) v Triti

(T) c nhiu trong H 2O l ngun nguyn liu v tn.


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Sn phm ca phn ng nhit hch khng c tnh phng x khng gy nhim mi trng.Ngun gc mt tri v ngi sao phn ng nhit hch.

iu kin xy ra: trong mi trng nhit rt cao c 50 triu oC 100 triuoC

Mt s hnh nh minh ha:

Cu hi t ra vi Ngun nng lng mt tri ?

Bom H - V kh ht nhn Cc quc gia thuc vng in m c v kh ht nhn !

CHC CC EM N TP HIU QU V T KT QU CAO NHT TRONG KTHI TUYN SINH I HC 2014

[email protected] - [email protected]

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