1. Chapter 4, section 4 Chapter 24
Nuclear Chemistry
Chapter 4, section 4
Chapter 24

2. Atomic Structure Review
Atomic # = # of Protons
# of Neutrons = Mass # - Atomic #
Isotopes have different #’s of neutrons
Isotope notation: Carbon-12 = C
Nucleon: General term for all protons & neutrons
Strong Nuclear Force: Short-range force among nucleons
Increases with shorter distance
Not the same as an electric force 12 6

3. Discovery In the 1900’s, only 3 radioactive elements were identified
Today, it is known that all elements after bismuth (83) are radioactive
The larger the atoms are, the more easily they “fall apart”

4. Stable vs. Unstable Nuclei
Nuclei can be stable or unstable
Stable nuclei do not spontaneously change
Unstable nuclei spontaneously change to become nuclei of different elements (the number of protons change)

5. Transmutation
Unstable nuclei are naturally “built wrong” and “fall apart”
The process by which one element becomes another is called transmutation -the nucleus’ number of protons is changed

6. Radioactivity (breaking down of nucleus)
Radioactivity of an atom depends on the ratio of neutrons (n) to protons (p+)
# n
# p+

7. Band of Stability Which atoms are stable?
A small atom (atomic # less than 20) is stable if its N/P ratio is very close to 1/1
A large atom (atomic # 20 or more) is stable if its N/P ratio is very close to 1.5/1
Predict the stability of the following:
Carbon-12
Hydrogen-3
Mercury-200
Uranium-238

8. Types of Radiation
(1min16sec)
During radioactive decay, unstable atoms lose energy by emitting radiation
The three most common types of radiation are alpha (α), beta (β) & gamma (γ)

9. alpha (α) particles Po  Pb + α
The symbol for an alpha particle is α where 4 is the mass and 2 is the charge
These particles are low in energy (they can’t even penetrate foil)
If these particles are emitted from an atom, the number of protons decreases
Alpha particles are never emitted with beta particles
Example: 4 2
Po  Pb + α
210 84
206 82 4 2

10. beta (β) particles C  N +
The symbol for a beta particle is β where 0 is the mass and -1 is the charge
These particles are higher in energy than alpha particles (they can penetrate skin)
If these particles are emitted from an atom, the number of protons increases
Beta particles are never emitted with alpha particles
Example: β -1
C  N + 14 6 7 -1

11. Gamma (γ) particles U  α + Th + 2 
The symbol for a gamma particle is γ where 0 is the mass and 0 is the charge
These particles are high energy electromag waves
They have no mass or charge
They have higher energy than beta particles- they are blocked only by thick lead or thick concrete
They are used to treat cancer if used “properly”
Usually emitted with alpha or beta particles
Example:
U  α Th 
238 92 4 2
234 90

12. Positron or Electron Capture
If positrons ( e) are emitted, the number of protons decreases (if something is emitted, it will be on the PRODUCT side of the equation)
If electrons ( e) are captured, the number of protons also decreases (if something is captured, it will be on the REACTANT side of the equation)
When a neutron is captured or emitted, use the symbol ( n) 1 -1 1

13. Fission and Fusion Nuclear Fission Nuclear Fusion
The splitting of a large atom into smaller ones
Does not normally occur in nature – Man-generated and used in nuclear in power plants
Requires little energy
Releases a lot of energy
The fusing of lighter atoms into a larger one
Occurs in stars (Ex: the sun)
Requires a lot of energy
Releases 3 to 4 times more energy than fission rxns