The Nucleus and Nuclear Chemistry
Z : atomic number = # of proton A : mass number = proton + neutron
,Z=Z',AA' isotope
nuclidep. n. :nucleons nucleus
XAZ
XX AZA
Z'':
Neutron-proton ratio
Neutron-proton ratio and Nuclear stability
n/p=1 n/p>1 ~5:3
Z>83,Z>83(radioactive element)
pn np
Stable Nuclide
Z A-Z Stable Nuclide Examples Even Even 168Even Odd 57Odd Even 50Odd Odd 4
Magic number (Z): 2, 8, 20, 28, 50, 82 ,126He O Ca
Doubly magic 10 isotopes
PbU
PbTh PbU
SnHe
20782
23592
20682
23220682
23892
50
42
N B Li H
Na F
Ti C
O C
147
105
63
21
2311
199
4722
136
168
126
cosmic abundance and nuclear stability
Light elements are more abundant than heavy elementsEven atomic number are more abundant than odd atomic number
(H),86%mass number
Magic number 2, 8, 20, 28, 50, 82(126 neutron)He O Ca Pb(114 protons)
Shell model of the nucleus :p, n exist in levels (shells)Analogous to the shell structure of electron
particle stable nuclei2 protons2 neutrons
82 protons208-82=126 neutrons RaHeTh
ThHeU22688
42
23090
23490
42
23892
+
+
He42 {
Pb20882
Radioactivity
Excited state
Emissi-on
ECelectron capture
Antine-utrino
neutrino
neutron
Too smallproton
Too Smallpositron
Too largebeta
alphaHeRaRa 4222286
22688 +
epn 0111
10 + eNC
01
147
146 +
nep 1001
11 + AreK
4018
01
4019 +
enp 0110
11 + eMoTc
01
9542
9543 +
242
42
+He 83>e01
01
ZN
e0101
+
H1111
nn 10
00
00
ZN
ZN
00;h
decay ray
1~ 0.001nm wavelength 10-12m
X-ray
Wavelength > 1nm (lifetime~10-9s)
hXX AZAZ +
* 009943
9943 + TcTcm
Excited
state
Ground
statem: metastable
XE AZ 1
2E
1
2
3 1
2
3
*42 X
Az
XAz42
E1-E2=1+2+3=2+3=3
Excitedstate
Groundstate
eXeI
PaTh
ePaTh
XX AZAZ
01
13154
13153
01
23191
23190
01
23491
23490
011
+
+
+
+
+
3Mev =>
- 0.5mmAl 0.015mmAl
(1)Electron emission
neutron proton +e-
Emitted along a continuous spectrum of energies
0max ( nucleide )
ray
, antineutrinoparticle()
neutral: massless particle
Antineutrino
Neutrino
0101
( )QE AZ1
E2
11 +
22 +
33 +
44 +
1
2
3
4
5
6
QAZ 1+
decay(electron emission,positron emission, electron capture)
Ray ,5~11cmAl 1~10MeVray100excited state lifetimensecnanosecisomeriosmeric transition
decay z > 83 A > 200 (nuclide)
that is too heavy
4 242
42 + XX
AZ
AZ
single energy or one of a few specific energy
existence of energy level within the
nucleus
,(1-10MeV )
10-3 mmAl
)(4222688
23090
42
22888
23290
HeRaTh
RaTh
+
+ particle -ray particle +2 change
D
8 1 g D 2500
T :Radioactive t1/2 =12.3 year
n+Li
MeVHeTslownLi
slownHeTfastnLi
8.4)(
)()(42
31
10
63
10
42
31
10
73
+++
+++
Shieldheat exchange
Magnet shieldblanket plasma
Li+ n + T
( )H21
( )H31
() ()60Co5.26222Rn()30.82
=A= N ) : N )
:1n (Nt /N0) = - t 1/2 = 0.693/
(C-14) C-14
14N 14C
14C/12C 1/101 2 14C
14C573014C15.3 disintegration/min . g
14
Counter
Resistance
high voltage
Argon gas
m
window
particle
HeLiBn
ArAr42
73
105
10
(g)particleenergyhigh
(g)
++
+ + e
Ar, gas
n BE3 added
Geiger counter
Geiger counter
HeLiBn
ArAr42
73
105
10
(g)particleenergyhigh
(g)
++
+ + e
Scintillation counter
photocathode photomultiplier tube
photocathode
photoelectric-sensitive surface
window
,, rays
Phosphor
NaIElectron Beam
ZnS
NaI + ThI
Nuclear Binding Energy
E = mc2
1.6x1014 g/cm3
(nucleus) 10-13 cm (atom)10-8 cm
Coulomb force = k (q1.q2) / r 2
nuclear force 30~40 x coulomb force() a distance of about 10-13 cm
Binding Energy per Nucleon
MeVCaMeVOMeVHe 55.8:00.8:14.7: 4020168
42
Nuclear Binding Energy
mass of atom 1 joule=1 kg m2/sec2
Difference in mass 1 amu=1.6605655 x 10-27 kg = 931.5017 MeV
39.96259 amu n: 1.008665 amup: 1.007825 amu.
++ + npe
Ca4020
Nuclear Binding Energy
m =39.96259 (20x1.008665) ( 20x1.007825)=0.36721 amu
E =0.36721 x1.6605655 x (2.9979 x108 m/sec)2x10-27
=5.4804 x 10-11 J = 342.06 MeV
1 MeV = 1.6021892 x 10-13 J
1 amu = 931.5017 Me VBinding Energy per nucleon:
40~100 (Fe ,Co ,Ni) -> Highest Binding E/ nucleon
nucleonMeV5515.84006.342
Nuclear Binding Energy
(8x1.67493 x 10-24 )+(8 x1.67262 x10-24 g) =2.67804x10-23 g
2.65535x10-23 g
m = -2.269x10-25 g or -0.1366 g/mol ( x 6.02 x1023 )
E= mc2 =(-1.366 x 10-4 kg/mol )(3.00 x108 m/s)2
= -1.23 x 1013 J/mol= -2.04 x10-11 J/nucleus (1Mev =1.60 x10-13 J)= -1.28x102 MeV
pnO 1110
168 88: +
nuleon8.00MeV
16101.28 2 =
:168O
Nuclear Fission
1938 Discovered by Otto HalmFritz Strassman UBa,
nKrBa
nZrTeUn103
9136
2142
56%3~2
10
9740
13752
23592
10
++
++ +
nSrXe
enCeZr
nKbCs
10
9038
14354
01
10
14058
9440
10
9037
14455
3
62
2
++
+++
++
83
OU
enrichment over 200 isotopes35 different elementsU2.4
nBaKr 1014156
9236 2++
Nuclear Fission
236U 14090
Subcritical , enough n are lost UChain reaction
Critical , maintain a count of fissions ,U 2.4,
mass large enough 1U 1 n (effective)
Super critical , n multiplies # of fission
nMoBaCf 10106
42142
56252
98 4++
430(17%) 100(20%)
20 metric tons
Light water reactors
Control rod
Fuel
Coolant (water)
H2O (neutron moderator)
Light water::H2O coolant and moderator350 150atm
D2O graphite
1.Fuel
U3O8 enriched 235U 2~3%
235U 0.7%
Zr coating
3.Moderator
H2Ographite
U
Light water H2Oheavy water D2OGraphite C
2.Control System
B (Boron) or Cd
4273
10
105 LinB ++
Breeder Reactor238
U 235
U232Th 374.1C
500C
fast breeder ( liq. metal Na ) (881 o c )neutron need not be moderated
(heat conducting better)
nucleonfastUnU 2399210
238 +
EnergynproductfissionnPu
PuNp
NpU
++ +
+
+
10
10
23994
01
23994
23993
01
23993
min2423992
3~2
0123391
min2223390
10
23290 + + PaThnTh
0123392 +U
)(239 fatalpoisonousPu
27
PuU
Pu
Pu
U
Nuclear Fusion
73%26%1%
eHeHHe
H2HeHeHe
HeHH
eHHH
01
42
11
32
11
42
32
32
32
21
11
01
21
11
11
++
++
+
++
nHHH 1042
13
21 ++
( )()H21
:
:13cm
Sun :
(plasma)
()
=>
H21 13cm7( 107 K)
++ 0142
1011 24
7
HeH k
Nuclear Fusion
Atomic Bomb
,
(ICRU)(SI)
:1.(activity)
() (Bq) :
1(Bq)=1/60Co ()
2.(Absorbed dose) D
() (GrayGy)
1(Gy)=1/ rad= 10-2 /
//(mGy/h/(Gy/h)
3.(dose equivalent) HT
( n)
(Q)2.1(Sv)
H()=D()XQ
(mSv)(Sv) Q 235226
/(mSv/y)/(Sv/h)
4.(effective dose equivalent)HE
()()(WT)(HT)(WT)(HE) HE(Sv)(HE)2(mSv)(2.4mSv)
rad. (radiation absorbed dose)
amt of radiation that deposits 1x10-2J of energy 1 kg of tissue.
(1rad) (1rad)
RBE Relative Biological effectiveness
measure the relative biological damage caused by radiation.
US system: curies (Ci) 1Ci=3.71010dps()
SI unit : becquerel (Bq) 1Bq=1decomposition per sec. (dps)
Amount of energy (damage) in the radiation absorbed by living tissue
US : 1Rads (Radiation absorbed dose)=0.01J/kg Tissue
SI : 1Gray (Gy)=1J/kg of tissue
Amount of biological damage /quality factor : (penetrating ability)
- -radiation =1
p- n- (low energy) =5
p- n- (high-energy) =20 or -particles
Relative Biological Effect (RBE)Relative effectiveness of the radiation in causing damage
Biological effect of radiation
US : rem (roentgen equivalent man) = rads quality factor
SI : Sv (sievert) = Gray quality factor
Background radioactivity : 200mrem/year
millirem (mrem)
20
10
1X
2.1
ICRP-26(1977)
RBE 1 for dose ratetotal dose type of tissue 10 for H fast neutron=51. x-ray -ray . (ions)2. 5 slow neutron 20 heavy aton.
relate various kind of radiation in
terms of biological destruction.
rems (roentgen equilivant for man)
rems = rad x RBE
0.1-0.2 rem
background radiation
()
0-25 rem
25-50
100-200
500 30
1000 30 100%
X- ~20-40 millirem
0.5 rem 500 millirem
5 rem
40K 21mrem
0.3mrem
Radioactive
Falloni 4 mrem
air 5
earth (47)
cosmic ray 52% 100 mrem (50)
X- 43% 80 mrem (61)
U 2% 4
??? 3% 6
0.14% 0.3 mrem
TV 0.02% 0.04 mrem
Building 3 mrem
waterial
ray + H2OH2O++e-
H2O++H2OH3O++OH
OHradical free radical
One or more unpaired electron
Somatic damage :affects the organism
During its own lifetime burn ,cancer
Genetic damage :genetic effect
Genes chromosones
Bone marrow ,blood forming tissue
Lymph nodes
leukemia
SI unit becquerel 1 nuclear/disintegration/sec
Old curie 1g Ra -226 3.71010 disintegration/sec
5.0 millicurie Co=5.010-33.71010
=1.8108 disintegration/sec
ray damaged not limited to the skin penetrating
stop by skin
penetrate 1cm