Nuclear Chemistry

Alpha rays ():
Beta rays ():
Gamma rays (
•Ernest Rutherford
•1871-1937
2

0.01 mm 1 mm 100 mm
Pieces of lead
3

(Z) =
(A) = +
= (Z) +
Mass Number
Atomic Number
A
Z
X
Element Symbol
4

Particle Symbol Nuclear
symbol
Proton p +
1
H 1 p
1 1
Neutron n 0
1
n
0
Electron e -
0
e
1
Alpha
4
2
Beta
0
1
Positron 0
4 2He
0 1e
0 1e
1
5

74
33
As 60
27
Co
226
88 Ra 15
32 P
59 Fe
24 Na
99 Tc
3 H
Strontium-90 Iodine-131 Carbon-6
6

ISOTOPES
1
1 H 2 1 H 3 1 H
12
6 C 13 6 C 14 6 C
235
92 U 238
92 U
7

MASS SPECTROSCOPY
m
B
2
E
qr
8

Balancing Nuclear Equations
1. Conserve mass number (A).
235 U
92
+ 138
0
55
Cs
1
n
+ 96 37
Rb + 2 1
n 0
235 + 1 = 138 + 96 + 2x1
2. Conserve atomic number (Z) or nuclear charge.
235 U
92
+ 138
0
Cs
55
1
n
+ 96 37
Rb + 2 1
n 0
92 + 0 = 55 + 37 + 2x0
10

212
Po alpha 212 Po.
alpha particle -
4
He
2
or
4
2
212
Po 4
He + A X
84 2 Z
212 = 4 + A A = 208
84 = 2 + Z Z = 82
212
Po 4
He + 208 Pb
84 2 82
11

12

13

222
88
Ra
4
2
He
218
86
Rn
14

15

16

17

18

n/p
beta decay
X
‣ (stable isotope)
(Radioisotope)
(Radioisotope)
Y
‣ p < 20 n/p = 1
‣ 21 < p < 83 n/p >1
‣ p > 83
n/p
positron decay or electron capture
19

-FILM BAGGES
20

- GEIGER-MULLER COUNTER
-
21

-CLOUD CHAMBER
(Cloud chamber)
cloud chamber photograph of pair production
22

(NATURAL RADIOACTIVITY-HALF-LIFE)
23

HALF-LIVES OF VARIOUS NUCLIDES
Nuclide Half-life Type of decay
Th-232 1.4 x 10 10 yr Alpha
U-238 4.5 x 10 9 yr Alpha
C-14 5730 yr Beta
Rn-220 55.6 sec Alpha
Th-219 1.05 x 10 –6 sec Alpha
24

25

(OBJECT DATING)
14
N + 1 n
14
C + 1 H
7 0 6 1
14
C
14
N + 0
6 7 -1
t ½ = 5730 years
26

RADIOCARBON DATING
% C-14 (compared to
living organism)
Object’s age (in years)
100% 0
90% 870
80% 1850
60% 4220
50% 5730
40% 7580
25% 11,500
10% 19,000
5% 24,800
1% 38,100 27

(OBJECT DATING)
Uranium-238 Dating
238
U
206
Pb + 8 4 + 6 0
92 82 2 -1
t ½ = 4.51 x 10 9 years
-
28

- (NUCLEAR FISSION)
+ energy!!
?
29

235
U + 1 n
90
Sr + 143 Xe + 3 1 n + Energy
92 0 38 54 0
30

+
31

o U-235
o Cd B
o Moderator
H 2 O D 2 O
o
o
32

- (NUCLEAR FUSION)
33

(RADIOISOTOPES IN MEDICINE)
• (tracer)
•
24
Na, t ½ = 14.8 hr, b emitter, blood-flow tracer
•
131
I, t ½ = 14.8 hr, b emitter, thyroid gland activity
•
123
I, t ½ = 13.3 hr, g-ray emitter, brain imaging
•
18
F, t ½ = 1.8 hr, b + emitter, positron emission tomography (PET)
•
99m
Tc, t ½ = 6 hr, g-ray emitter, imaging agent
Brain images with 123 I-
labeled compound
34

- TREATMENT RADIOTHERAPY
Co-60
35

-
36

-
37

-SMOKE DETECTOR
38

BIOLOGICAL EFFECTS OF RADIATION
The amount of danger to humans of
radiation is measured in the unit rems.
Dose (rems)
Probable outcome
20–100
100–400
500+ Death
Decreased white blood cell count;
possible increased cancer risk
Radiation sickness;
increased cancer risk
39

Biological Effects of Radiation
Radiation absorbed dose (rad)
1 rad = 1 x 10 -5 J/g of material
Roentgen equivalent for man (rem)
1 rem = 1 rad x Q Quality Factor
-ray = 1
= 1
= 20
40