1. Nuclear Chemistry
Lesson 1

2. Atomic Notation Sr 90 38 Recall, we learned atomic notation.
A nuclide is the nucleus of a specific atom.
The radioactive nuclide strontium-90 has 90 protons and neutrons. The atomic number is 38. Sr 90 38

3. Radioisotopes
The nuclei of unstable isotopes gain stability by undergoing changes and emitting large amounts of energy (radiation)
Nearly all isotopes with atomic number of 84 or greater are unstable

4. Band of Stability and Radioactive Decay

5. Transmutation The conversion of one atom to another is transmutation
Artificial Transmutation – particles bombard the nucleus of an atom forcing a change.
Natural Transmutation – the nucleus of an atom undergoes radioactive decay due to an imbalance between the number of protons and neutrons in a nucleus. Unstable atoms will decay until they create more stable atoms.

6. Mass Defect (Deficit)
Some of the mass in the nucleus can be converted into energy (less than the mass of an proton)
Shown by a very famous equation!
E=mc2
Energy
Mass
Speed of light (a rather large number) ≈ 3 x 108 m/s
In all nuclear reactions, some amount of
mass is lost and converted into energy

7. Mass Defect
Difference between the mass of an atom and the mass of its individual particles
amu
amu

8. Nuclear Reactions vs. Normal Chemical Changes
Nuclear reactions involve the nucleus. The nucleus opens, and protons and neutrons are rearranged.
The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy
“Normal” Chemical Reactions involve electrons, not protons and neutrons, therefore, comparatively little energy is gained from these reactions.

9. Types of Radiation Alpha (ά) – a positively charged helium nucleus
Beta (β) – a.k.a. electron
Gamma (γ) – pure energy; called a ray rather than a particle – has no mass or charge

10. Other Nuclear Particles
Neutron
Positron – a positive particle, same size as an electron
Proton – usually referred to as hydrogen-1
And many other elemental isotopes

11. Charge of Radiation Types
Alpha particles have a +2 charge, and beta particles have a –1 charge. Both are deflected by an electric field.
Gamma rays are electromagnetic radiation and have no charge, so they are not deflected.

12. Penetrating Ability
Video

13. Behavior of Radiation
Since alpha particles have the largest mass, they are the slowest-moving type of radiation.
Gamma rays move at the speed of light since they are electromagnetic radiation.

14. Alpha Radiation
An alpha particle (a) or helium nucleus (42He) is emitted
Each particle contains 2 protons, 2 neutrons and has a +2 charge (not usually written)
23892U  23490Th + 42He
Note that the equation is balanced.
The sum of the mass numbers & atomic numbers are equal.

15. Beta Radiation A beta particle (b) or electron (0-1e) is emitted
A neutron breaks apart into a proton, which remains in the nucleus, and an electron, which is released
146C  147N + 0-1e
Note that the equation is balanced.
The sum of the mass numbers & atomic numbers are equal.

16. Gamma Radiation
A gamma particle (g) or high energy photon is emitted (light)
Gamma rays have no mass, no p+ and no no so they do not alter atomic mass or atomic number.
It is PURE ENERGY which explains the large penetrating power of g rays.
They are often emitted along with alpha or beta particles
23090Th  22688Ra + 42He + g

17. Electron Capture
A few large, unstable nuclides decay by electron capture. A heavy, positively charged nucleus attracts an electron.
The electron combines with a proton to produce a neutron.
Lead-205 decays by electron capture. Pb
205 82 e -1 Tl 81 +

18. Balancing Nuclear Reactions
The total of the atomic numbers (subscripts) on the left side of the equation must equal the sum of the atomic numbers on the right side.
The total of the atomic masses (superscripts) on the left side of the equation must equal the sum of the atomic masses on the right side.
After completing the equation by writing all the nuclear particles in an atomic notation, a coefficient may be necessary to balance the reaction.
Use a particle or isotope to fill in the missing protons and neutrons.

19. Practice Problem 18579Au  18177Ir + 42He
Write the nuclear equation for the alpha decay of gold-185.
18579Au  18177Ir + 42He

20. Practice Problem
Fill in the blank.
21484Po  ___ e + g
214At 85

21. Practice Problem Fill in the blank. 222Rn 86
21484Po He e  ___________

22. Practice Problem
What radioactive isotope is produced in the following bombardment of boron?
10B He _____ + 1n
13N 7