1. Nuclear Chemistry

2. Outline Background/Introduction Spontaneous Nuclear Reactions
Types of Radioactive Decay
Radioactive Half-Life
Stimulated Nuclear Reactions
Nuclear Fission
Nuclear Fusion

3. Nuclear Chemistry - Background
Traditional Chemistry
Reactions occur due to interactions between valence electrons (surrounding nucleus)
Late 1800s – Early 1900s  New Developments
Discovery that Uranium emits radiation (Henry Becquerel)
Amount of radiation emitted is proportional to amount of element present (Marie Curie)
“Radioactive” substances = radiation-emitting (Curie)
Radioactivity = a inherent property of certain ATOMS, as opposed to a chemical property of compounds (Curie)
Birth of nuclear chemistry

4. Video: Early (Mis)uses of Radium
A radioactive element discovered in 1898 by Curie
Found to glow in the dark!
Many (at the time) thought it had health benefits
Radium Toothpaste
For video, see below URL: For more complete list of “quack” cures, see below URL:

5. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Loss, gain, sharing of valence electrons
Formation of compounds
(Recall the different reaction types)
Affected by temperature, pressure,
presence of other atoms
Changes in nucleus
Transformation of one element
into a different isotope or a
different element altogether
Unaffected by temperature,
pressure, presence of other atoms

6. Atomic Structure Review
Isotopes: variants of atoms of a particular chemical element, which have differing numbers of neutrons (e.g. Carbon-12, Carbon-13, Carbon-14, etc.)

7. Nuclear Stability How can a stable nucleus exist? Nuclear Force (1934)
Net positive charge in nucleus surrounded by negative charges (electrons)
Electrostatic force
Opposite charges attract
Like charges repel
Why doesn’t the nucleus break apart?
Nuclear Force (1934)
Force between protons and neutrons than binds nucleus together within atom
Very strong (must be!)

8. Which Elements/Isotopes Are Radioactive?
Based on the nuclear force and nuclear stability
More protons in nucleus  more neutrons needed to bind nucleus together
Critical Factor = Neutral-to-Proton Ratio
Neutron-to-Proton ratios of stable nuclei increase with increasing atomic number
Unstable neutron-to-proton ratio = RADIOACTIVE
Nuclei with atomic numbers ≥ 84 = ALWAYS Radioactive
Very large nuclei!
Neutron-to-proton ratio always unstable

10. Spontaneous Nuclear Reactions

11. Radiation and Radioactive Decay
Unstable (radioactive) nuclei emit radiation (energy) in order to become more stable
Radioactive Decay – occurs when a nucleus spontaneously decomposes in this way
3 Common Types of Nuclear Reactions
Alpha Radiation
Beta Radiation
Gamma Radiation

12. Alpha (α) Radiation

13. Alpha Radiation: Nuclear Equation
Emission of 2 protons and 2 neutrons (as an alpha particle, ) from radioactive atom’s nucleus
Atom’s atomic mass decreases by 4 units
Atom’s atomic number decreases by 2 units (a different element!)

14. Beta (β) Radiation

15. Beta Radiation: Nuclear Equation
Conversion of a neutron into a proton and an electron, followed by the emission of the electron (beta particle) from the nucleus
Atom’s atomic mass does NOT change
Atom’s atomic number increases by 1 units (a different element!)

16. Gamma (ϒ) Radiation
Emission of electromagnetic energy from an atom’s nucleus
No particles emitted
Often occurs during α and/or β decay
Example: X-rays emitted during β-decay of cobalt-60 (above)

17. Uranium-238: Radioactive Decay Chain

18. Practice: WE DO
Write a nuclear equation for the β-decay of francium-234
Write a nuclear equation for the α-decay of radium-235
Write a nuclear equation for the ϒ-decay of uranium-239

19. Practice: YOU DO
What isotope is present after Po-210 undergoes 2 consecutive alpha decays, followed by a beta decay, followed by another alpha decay.

20. Half-Life (T1/2) = The amount of time necessary for one-half of a particular radioactive sample to decay

21. Different Elements  Different Half-Lives
Data for most
stable isotope of element

22. Half-Life Problems Half-Life Formulas
Can be completed without the below formulas!
Conceptual knowledge of half-life is sufficient
Half-Life Formulas
Fraction remaining = (n = # of half-lives elapsed)
Amount remaining = Original Amount * Fraction Remaining

23. Practice: WE DO
The half-life of radium-226 is 1600 years. How many grams of a 0.25 gram sample will remain after 4800 years?

24. Practice: YOU DO
How many days does it take for 16 g of palladium-103 to decay to 1.0 g? The half-life of palladium-103 is 17 days.
The half-life of thorium-227 is days. How many days are required for 75% of a given amount to decay?

25. Stimulated Nuclear Reactions

26. Nuclear Fission Neutron fired at atom’s nucleus
Energy of neutron “bullet” causes target element to split into two (or more) elements that are lighter than the parent atom
Unpredictable composition of products
Energy released!
More neutrons released!
RESULT?  SEE NEXT SLIDE

28. Nuclear Fission Chain Reactions
Nuclear Fission Power
(Controlled Nuclear Fission)
Nuclear Fission (Atomic) Bomb
(Uncontrolled Nuclear Fission)

29. Nuclear Fission (Atomic) Bombs
Fuel Core (B)
Two subcritical masses of plutonium
Each contains not enough fissionable material to sustain nuclear fission
Neutron source (radioactive isotope) in separate compartment
Detonation of outer casing of TNT (A)
Two plutonium masses brought together to form supercritical mass
Mass now contains enough fissionable material to sustain nuclear fission!
Neutrons brought to speed necessary to initiate nuclear fission

30. Nuclear Fusion
Reactions in which two or more elements “fuse” together to form one larger element (heaver isotope formed from lighter isotopes)
Requires extremely high heat (lots of energy!) and pressure
Analogy: trying to squeeze an unopened can of Coke into a little ball without spilling any Coke
Lots of energy is released!
Example: Fusion of 2 hydrogen isotopes (deuterium and tritium) into helium

31. Nuclear Fusion (Hydrogen) Bombs
Central core (B) of trillions of deuterium and tritium isotopes
Surrounded by small atomic (fission) bombs (A)
Detonation of atomic bombs provides energy and pressure for fusion of hydrogen isotopes into helium
LOTS of energy released in this process!
Atomic bombs (nuclear fission) used to initiate nuclear fusion
Fusion itself  energy release
Release of neutrons accompanying fusion triggers fission of bomb casing (C), which is made of Uranium!

32. Nuclear Fusion (Hydrogen) Bombs
Energy released = over 10 times greater than fission (atomic) bomb
Has never been used in warfare
Neutron bomb = Hydrogen bomb without uranium casing
Less explosion, due to lack of fission of casing
Large quantity of neutrons propelled outward (neutron radiation) and captured by nuclei of substances they encounter
Results: * Neutron radiation induces radioactivity in most substances it encounters
* Massive radiation without massive blast
Targets: * Potential H-bomb survivors (e.g. tank drivers, stronghold inhabitants, etc.)
* Ballistic missiles (intense neutron flux damages electron components)

33. Nuclear Fusion in the Sun
Energy is released from these fusion reactions that we receive as LIGHT and HEAT!
NOTE: 3 hydrogen-1 atoms required (total), yet only 2 produced
The Sun is running out of fuel (hydrogen-1 atoms)!

34. Controlled Nuclear Fusion on Earth?
Advantages over nuclear fission
More energy created
Very little dangerous radiation released
Potential Source = Water (and not much of it)!!
Main Challenge
Need to find way to bring small sample of deuterium and tritium to very high temperature and pressure WITHOUT detonating atomic bombs
Subject of much current research in physics and chemistry