1. Radioactive!…radioactive!
Nuclear Chemistry
Radioactive!…radioactive!
Radiation is NOT some mysterious unknown force. It is just a particle or beam light given off by an unstable element trying to become stable.
Protons are all positive how do they stick together in the nucleus?
The Strong Nuclear Force holds them together with the neutrons acting as a sort of glue.
Nuclei with too many protons or too few neutrons under go spontaneous disintegration into smaller particles ejected at high speeds from the nucleus we call this particle or light:
Radiation:

2. Uses of Nuclear Power Nuclear Subs SUN FUSION! Nuclear Power
Some high resolution
Medical Imaging: CAT scan
Smoke Detectors
Sterilize Meat/Produce
Spacecraft: Cassini

3. More Dangerous Uses of Nuclear Power
10 largest nuclear bomb tests (all larger than Hiroshima/Nagasaki)
Ban on Nuclear testing?
Atomic bombs (fission)
Chernobyl
Nuclear Power Disasters!
H bombs aka thermonuclear (fusion & fission)

4. REVIEW Neutral Atom: SKETCH & LABEL
Shell or Orbit
IMPORTANT: NUMBER OF PROTONS DETERMINES WHAT ELEMENT YOU ARE AKA ATOMIC NUMBER!
ELECTRON – negative, mass nearly nothing 0 AMU
(1/3000)
*PROTON – positive, same mass as neutron (“1” AMU)
NEUTRON – neutral, same mass as proton (“1” AMU)
Nucleus

5. Neutral _________Atom
Hydrogen
Proton
Electron
Hydrogen has one proton, one electron and NO neutrons weighs 1 AMU

6. ________Atom Helium Lithium Proton Electron Neutron
Neutron
Helium has two electrons, two protons and two neutrons so it typically weighs 4 AMU. But here…
It is He-5 a radioactive version of He. Unstable it gives off an electron from a neutron transmuting it into a proton n=e-+ p+ becoming a new stable element called: ^

7. Nuclear Reactions vs. Chemical Reactions
“Normal” Chemical Reactions involve:
electrons and electromagnetic force,
Nuclear reactions involve the:
nucleus only and ignore valence e-
When the nucleus changes the energy that holds the nucleus together called binding energy from the ‘strong’ force. is released:
This is what causes the radiation and possibly the big kaboom.

8. Binding Energy/Mass Defect
In nuclear reactions, a tiny amount of the mass seems to vanish. Called the “mass defect”
Einstein figured out where it went and his formula helped create both nuclear weapons and nuclear power
E=mc2
Energy
Mass
Speed of light (a huge number which is how a tiny amount of energy can create a massive energy release)

9. 3 Main Types of Nuclear Radiation & Symbols
Symbols you need to memorize
Alpha (ά) – a positively charged helium nucleus NO electrons.
Beta (β) – an electron
Gamma (γ) – pure electromagnetic energy; called a ray rather than a particle
Mass
proton
Mass
charge
Mass
charge

10. More Nuclear Particles!
Mass
Neutron (proton + electron)
Positron – a positive electron: *formed when a proton decays into a neutron.
Proton – usually referred to as hydrogen-1 (neutron/positron together)
Bombarder/Ejected Particle: Any other elemental isotope “X”left from the nuclear reaction
charge
Mass
charge
Mass
protons
charge
Mass
protons

11. Radiation Penetrating Ability Sketch and label sizes
largest
smallest
Med
Size relates to penetrating power. Label the smallest,med and largest particle.

12. 2 Main Nuclear Processes
Nuclear fission: a heavy radioisotope splits to form two more stable lighter ones.
Nuclear Decay is when this fission happens spontaneously.
Ex: Uranium to Radon to Lead.
Nuclear fusion: 2 lighter radioisotopes are forced together to form a more stable heavier one.
Nuclear Bombardment is when we intentionally do this by exposing a source to high speed/pressure radiation like in a super collider (or a star)
Ex Hydrogen + Hydrogen = Helium

13. Super Colliders: Bombardment/Fusion
Super colliders are large machines that accelerate particles to near the speed of light via magnets and then smash (bombard/fuse) them into other particles to create new elements and new particles.
4 New Elements!
Fission or Fusion:
The CERN particle accelerator is 5 miles across (16.7 miles long) and uses more power than 2 nearby cities!
CERN Restart:

14. 5 Steps to Write Nuclear Reactions
Reactants (starting materials – go on the left side of an equation)
Draw to…
Products (final products –go on the right side of an equation)
BOTH SIDES MUST BE EQUAL!! SO
On the side that changes, try to balance Atomic numbers and balance Mass numbers to see what is missing.
5. Write in using a particle and isotope to fill missing protons and neutrons amounts.

15. Nuclear Reactions: Decay
Alpha emission
Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2.
Nucleons aka nuclear particles like protons and neutrons are rearranged but must overall be conserved (go somewhere)

16. Nuclear Reactions: Decay
Beta emission
Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.
-1 neutron, +1 proton.
*A neutron BECOMES a proton + electron

17. Nuclear Reactions: Decay
Positron (0+1b): a positive ‘electron’ emission
207
Note that mass number (A) is unchanged and atomic number (Z) goes DOWN by 1.
*A Proton BECOMES a neutron + positron

18. Write a Nuclear Decay Equation!
Write the nuclear equation for the beta emitter Co-60.
*HINT Start with the reactant, then the products: radiation then the new isotope

19. Transuranium Elements
Elements beyond 92 (transuranium) are typically very radioactive so none exist naturally (anymore). They are “manmade” starting with an g reaction
23892U n ---> U + g
23992U > Np b
23993Np ---> Pu b
NEW!
NEW!

20. Nuclear Reactions: Bombardment
Beta: the capture of an electron by proton turns it into a neutron
Alpha /Others: The collision will be between a: target isotope and a: projectile (lighter particle) This will generally create 2 things:
Product : heavy isotope leftover
Ejected particle: whatever lighter part remains

21. Write a Nuclear Bombardment Equation:
What radioactive isotope is produced in the following bombardment of boron?
10B He ? n

22. Nuclear Fission

23. Half-Life: Nuclear‘Timers’
HALF-LIFE is the time that it takes for 1/2 a sample to decompose.
The half life of a radioactive isotope DOES NOT CHANGE.
ESSENTIAL for radioactive dating:
(No I don’t want to take uranium out to dinner)
This is the process of determining age from ratio of parent isotope: original radioisotope to
daughter product: more stable decay product

24. All Radioactive elements undergo Exponential Decay!
Decay of 20.0 mg of 15O.
What remains after 1 half-life?
10 mg
5 mg
What remains after 2 half-lives?
What remains after 3 half-lives?
2.5 mg

25. Kinetics of Radioactive Decay
So for each duration (half-life), one half of the substance decomposes.
Example 1: Ra-234 has a half-life of 3.6 days If you start with 50 grams of Ra-234
After 3.6 days >
25 grams
After 7.2 days >
12.5 grams
After 10.8 days >
6.25 grams

26. Special Halflife: Radiocarbon Dating
Radioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by neutrons in cosmic & solar radiation
14N + 1on ---> 14C + 1H
The C-14 is oxidized to CO2, which circulates through the plants via photosynthesis and the carbon cycle. So..
THIS MEANS ALL THE FOOD YOU EAT HAS C14 !
When the living thing dies, the C-14 is not replenished.
But the C-14 continues to decay with t1/2 = 5730 years.
So the remaining C-14 Activity of a sample can be used to date the sample making C14 particularly useful for living things!

27. Example Problem: Halflife
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?
Start HL WS