1. Nuclear Chemistry
Chapter 25

2. What do you think of when you hear Nuclear Chemistry?

3. History Henri Becquerel (1852-1908)
Originally thought sunlight caused uranium to radiate
Discovered the spontaneous radiation while waiting for a sunny day to test his theory
Marie Curie ( ) and her husband Pierre Curie ( )
Worked w/ Becquerel
Eventually showed that the rays were from uranium atoms
Came up with the term “radioactivity” to describe
History

4. Why Radioactive? Some isotopes are stable and others are not.
Nucleus is protons and neutrons
Protons are positive so they repel
Neutrons are only stable when near a proton
Some have:
Too many protons
Too many neutrons
Just plain too many
So they “fall apart”
Why Radioactive?

5. First 3 kinds of radiation found

6. First 3 kinds of radiation found

7. Summary of Radiation ALPHA BETA GAMMA Positive matter
Exactly like a Helium nucleus
BETA
Negative matter
Exactly like an electron
GAMMA
High energy wave
NOT matter so no charge
Summary of Radiation

8. Alpha Radiation- when a helium nuclei has been emitted from a radioactive source.
Types of Radiation

9. Beta Radiation – An electron resulting from the breaking apart of a neutron in an atom.
Types of Radiation

10. Gamma Radiation – a high-energy photon emitted by a radioisotope
Gamma Radiation – a high-energy photon emitted by a radioisotope. (electromagnetic radiation)
Extremely Dangerous!
Types of Radiation

11. Type of Radiation
Symbol
Mass
Nuclear Charge
Particle
Alpha  𝛼 
 4 amu
 2 +
  2 4 𝐻𝑒
 Beta  𝛽
  amu
 1 -
𝑒 −  
Gamma   𝛾  0

12. How can we use what we know?
Look for patterns
Try to explain the patterns
Test your ideas with known things
Use the pattern to figure out unknown things
Adjust as necessary!
How can we use what we know?

13. The blue ones have at least one stable isotope. Others do not!

15. How does this help? Chart helps predict type of decay
Too many neutrons?
Emit a beta particle to change a neutron to a proton and move closer to the band of stability
Just too big?
Emit an alpha particle to reduce size of nucleus
There are many types of decay, but chart helps give us targets when trying to manipulate elements to do what we want
How does this help?

16. Writing and Balancing Nuclear Equations
Mass numbers and charges are conserved (equal on both sides)
Example Alpha Decay
𝑃𝑢 → 𝑍 𝐴 𝑋 𝐻𝑒
Mass number of product A= ?
Atomic Number of product Z= ?
Reaction Product X = ?
238= A+4
94=Z+2
So… 𝑈 is the answer
Writing and Balancing Nuclear Equations

17. Writing and Balancing Nuclear Equations
Mass numbers and charges are conserved (equal on both sides)
Example Beta Decay
𝑃𝑢 → 𝑍 𝐴 𝑋 + 𝑒 − ( −1 0 𝛽 )
Mass number of product A= ?
Atomic Number of product Z= ?
Reaction Product X = ?
since beta decay is the break up of a neutron into a proton and an electron the mass # doesn’t change
Z will be one greater Z= 95
So… 𝐴𝑚 is the answer
Writing and Balancing Nuclear Equations

18. Practice Show the products of Bismuth -212 undergoing an alpha decay
𝐵𝑖 → 2 4 𝐻𝑒 𝑇𝑙
Now the Daughter thallium undergoes a beta decay
𝑇𝑙 → 𝑒 − ( −1 0 𝛽 ) 𝑃𝑏
Practice

19. Half-Life is the time required for half of the atoms in a radioactive sample to decay
Number of half-lives
Elapsed time
Amount of strontium-90 present
0 y
10.0g 1
29 y
5.00g 2
58 y
2.50g 3
87 y
1.25g 4
116 y
0.625g
Half -Life

20. Practice
Bandages can be sterilized by exposure to gamma radiation from colbalt-60, which has a half-life of 5.27 years. How much of a 10.0 mg sample of cobalt-60 is left after one half-life? Two half-lives? Three half- lives? How many years is 3 half-lives?
5.00mg; 2.50mg; 1.25mg; 15.81y
Half-Life