1. CHAPTER 22 Nuclear Chemistry
I. The Nucleus
(p ) II
III IV

2. A. Mass Defect
Difference between the mass of an atom and the mass of its individual particles.
amu
amu

3. B. Nuclear Binding Energy
Energy released when a nucleus is formed from nucleons.
High binding energy = stable nucleus.
E = mc2
E: energy (J)
m: mass defect (kg)
c: speed of light (3.00×108 m/s)

4. B. Nuclear Binding Energy
Unstable nuclides are radioactive and undergo radioactive decay.

5. Stable Nuclei

6. CHAPTER 22 Nuclear Chemistry
II. Radioactive Decay
(p ) II
III IV

7. A. Types of Radiation 2+ 1- 1+ Alpha particle () helium nucleus
paper 2+
Beta particle (-)
electron 1-
lead
Positron (+)
positron 1+
concrete
Gamma ()
high-energy photon

8. B. Nuclear Decay Numbers must balance!! Alpha Emission parent nuclide
daughter
nuclide
alpha
particle
Numbers must balance!!

9. B. Nuclear Decay
Beta Emission
electron
Positron Emission
positron

10. B. Nuclear Decay Electron Capture electron Gamma Emission
Usually follows other types of decay.
Transmutation
One element becomes another.

11. B. Nuclear Decay Why nuclides decay…
need stable ratio of neutrons to protons
DECAY SERIES TRANSPARENCY

12. B. Synthetic Elements Transuranium Elements
elements with atomic #s above 92
synthetically produced in nuclear reactors and accelerators
most decay very rapidly

13. Stop

14. C. Radioactive Dating
half-life measurements of radioactive elements are used to determine the age of an object
decay rate indicates amount of radioactive material
EX: 14C - up to 40,000 years 238U and 40K - over 300,000 years

15. Radiation treatment using
D. Nuclear Medicine
Radioisotope Tracers
absorbed by specific organs and used to diagnose diseases
Radiation Treatment
larger doses are used to kill cancerous cells in targeted organs
internal or external radiation source
Radiation treatment using
-rays from cobalt-60.

16. F. Others Food Irradiation  radiation is used to kill bacteria
Radioactive Tracers
explore chemical pathways
trace water flow
study plant growth, photosynthesis
Consumer Products
ionizing smoke detectors - 241Am

17. Half Life
The rate at which radioactive nuclides decay is dependent upon the amount of the nuclide present to begin with.
Decay rate is usually expressed in terms of half life, the amount of time it takes for half of a sample to decay.

18. Illustrative Example - 20 min. Half Life
Original sample
32 nuclei
After 20 min.,
half is left.
After another 20 min., one fourth is left.
One eighth is left after another 20 min.
Number of atoms
decayed:

19. Another Example

20. C. Half-life Half-life (t½)
Time required for half the atoms of a radioactive nuclide to decay.
Shorter half-life = less stable.

21. The half-life of cobalt-60 is 10. 47 minutes
The half-life of cobalt-60 is minutes. How many mg of cobalt-60 remain after minutes if you start with 10.0 mg?

22. C. Half-life
mf: final mass
mi: initial mass
n: # of half-lives

23. C. Half-life t½ = 5.0 s mf = mi (½)n mi = 25 g mf = (25 g)(0.5)12
Fluorine-21 has a half-life of 5.0 seconds. If you start with 25 g of fluorine-21, how many grams would remain after 60.0 s?
GIVEN:
t½ = 5.0 s
mi = 25 g
mf = ?
total time = 60.0 s
n = 60.0s ÷ 5.0s =12
WORK:
mf = mi (½)n
mf = (25 g)(0.5)12
mf = g