1. Nuclear Reactions

2. Nuclear Reactions vs. Normal Chemical Changes
NUCLEAR REACTIONS involve the NUCLEUS.
PROTONS and NEUTRONS are REARRANGED in the nucleus, releasing a tremendous amount of energy.
“Normal” CHEMICAL REACTIONS involve ELECTRONS, not protons and neutrons.

3. Why do Nuclear Reactions happen?
Nuclear Instability
The stability of a nucleus is dependent on the neutron to proton ratio (N:Z)
For light nuclei (elements 1-20), the N:Z ratio should be 1:1
For heavy nuclei (elements above 20), the N:Z ratio should be 1.5:1

4. Atoms that lie ABOVE the band of stability have TOO MANY NEUTRONS.
Atoms that lie either above or below the band of stability will undergo nuclear decay to achieve stability.
Atoms that lie ABOVE the band of stability have TOO MANY NEUTRONS.
Atoms that lie BELOW the band of stability have TOO MANY PROTONS.

5. Two Types of Nuclear Reactions
Fission – nucleus splits into smaller nuclei to become more stable.
Fusion – nuclei fuse into one larger nucleus to become more stable.

6. Uses for Nuclear Reactions
Fission:
atomic bombs (like those dropped on Hiroshima and Nagasaki).
Nuclear reactors
Fusion:
the sun (or any star)
Creating elements larger than Element 92 Uranium
Elements 1-92 occur naturally in the universe
Half-Life (Radiocarbon dating):
Using the known half-life of elements to determine the age of artifacts

7. Half-Life
Radioisotope: an unstable, radioactive atom that decays over time to become more stable.
Half-Life: the amount of time that it takes half of a radioisotope sample to decay.

8. Nuclear Decay
People at higher elevations, receive more radiation.
RADIATION: particles & electromagnetic waves released during nuclear decay.
Most radiation comes from the SUN & COSMIC RADIATION.

9. Nuclear Decay Products4 2 He or 
ALPHA particle: α
is a Helium-4 nucleus
has POOR PENETRATING ability – can be stopped by PAPER.

10. Nuclear Decay Products-1  or e
BETA particle: β
aka. ELECTRON or NEGATRON
has a negative charge
A NEUTRON emits a negatron and then BECOMES a PROTON +1  or e
POSITRON
aka. ANTIELECTRON
has a positive charge
A PROTON emits a positron and then BECOMES a NEUTRON
Penetrate BETTER than ALPHA particles, but can be stopped by an ALUMINUM sheet.

11. Nuclear Decay Productsg
GAMMA ray: γ
is a gamma PHOTON.
has GREAT PENETRATING ability – can ONLY be stopped by LEAD or CONCRETE.
is very DANGEROUS.
can be released with other forms of decay.

12. Nuclear Decay Products

13. Nuclear Equations Reactants Products
Yield
Nuclear equations must be BALANCED.
The sum of the MASS NUMBERS and the sum of the ATOMIC NUMBERS must be the SAME on both sides of the equation.

14. U Th + He Alpha Decay Reaction Mass # Change: decrease by 4
238 92
234 90 4 2
Mass # Change: decrease by 4
Atomic # Change: decrease by 2

15. C N + e Beta Decay Reaction Mass # Change: no change14 6 7 -1
Mass # Change: no change
Atomic # Change: increase by 1

16. Electron Capture Reaction
Cr e V 51 24 -1 23
Mass # Change: no change
Atomic # Change: decrease by 1

17. Positron Emission Reaction
Cr V e 49 24 23 +1
Mass # Change: no change
Atomic # Change: decrease by 1

18. g e e Nuclear Reactions He 4 2 -1 1 4 2 -1 +1 00 Radiation Type
Particle
Involved
Mass
Charge
Change in Mass #
Change in Atomic #
Alpha Decay 4 2
Decreases by 4
Decreases by 2
Beta Decay -1
N/C
Increases by 1
Positron Emission 1
Decreases by 1
Gamma Radiation 4 2 He -1 e e +1 g 00