1. Nuclear Chemistry
Chapter 28

2. Introduction to Nuclear Chemistry
Nuclear chemistry is the study of the structure of and the they undergo.
atomic nuclei
changes

3. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes
Reaction rate influenced by temperature, particle size, concentration, etc.
Reaction rate is not influenced by temperature, particle size, concentration, etc.

4. Radioactivity – some key terms
Isotopes – atoms of the same element with different numbers of neutrons
Radioisotopes – isotopes of atoms with unstable nuclei (too many or few neutrons)
Radioactive decay – when unstable nuclei lose energy by emitting radiation to attain more stable atomic configurations (spontaneous process)

5. Review of Atomic Structure
Nucleus
Electrons
99.9% of the mass but
1/10,000 the size of the atom
0.01% of the mass
Composed of protons (p+) and neutrons (n0)
Composed of electrons (e-)
Positively charged
Negatively charged
Strong nuclear force (holds the nucleus together)
Weak electrostatic force (because they are charged negatively)

6. mass # atomic # Chemical Symbols C A nuclear symbol looks like…
To find the number of neutrons, subtract the atomic number from the mass number.
mass # 14 C
atomic # 6

7. Nuclear Stability
An Isotope is completely stable if the nucleus will not spontaneously decompose.
Elements with atomic numbers 1 to 20 are very stable.
A 1:1 ratio of protons : neutrons (p+ : n0) makes an isotope very stable
Example: Carbon – 12 has 6 protons and 6 neutrons

8. Nuclear Stability
Elements with atomic numbers 21 to 82 are marginally stable.
A 1 : 1.5 ratio of protons : neutrons (p+ : n0)
Example: Mercury – 200 has 80 protons and neutrons

9. Nuclear Stability
Elements with atomic numbers > 82 are unstable and radioactive.
Isotopes with greater than 1.5 neutrons per 1 proton are unstable or radioactive
Examples: Uranium and Plutonium

10. Transmutation
Transmutation is the conversion of one atom of one element to an atom of a different element.
Alpha and beta decay cause this to occur.

11. α 4 mass 4 atomic 2 He Alpha Decay +2 protons
Alpha decay – emission of an alpha particle ( ), denoted by the symbol , because an α has 2 protons and 2 neutrons, just like the He nucleus. Charge is because of the
Mass of alpha particle is amu.
Alpha decay causes the number to decrease by and the number to decrease by .
This can be shielded by a sheet of paper He 4 2 +2
protons 4
mass 4
atomic 2

12. Alpha Decay
Example 1: Write the nuclear equation for the radioactive decay of polonium – 210 by alpha emission.
Step 3: Write the alpha particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass #
210 Po 84
206 Pb 4 He 2 82
Atomic #

13. Alpha Decay
Example 2: Write the nuclear equation for the radioactive decay of radium – 226 by alpha emission.
Step 3: Write the alpha particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass #
226 Ra 88
222 Rn 4 He 2 86
Atomic #

14. β e- e electron -1 electron no mass 1 Beta decay atomic
Beta decay – emission of a beta particle ( ), a fast moving , denoted by the symbol or β has insignificant mass ( ) and the charge is because it’s an
This occurs as a neutron changes into a proton by emitting the negatively charged beta particle
Beta decay causes change in number and causes the number to increase by .
These can be shielded by metal foil. e-
electron e -1 -1
electron no
mass
atomic 1

15. C e N Beta Decay 14 6 14 -1 7 Step 3: Write the beta particle.
Example 1: Write the nuclear equation for the radioactive decay of carbon – 14 by beta emission.
Step 3: Write the beta particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass # 14 C 6 14 e -1 N 7
Atomic #

16. Zr e Nb Beta Decay 97 40 97 -1 41 Step 3: Write the beta particle.
Example 2: Write the nuclear equation for the radioactive decay of zirconium – 97 by beta decay.
Step 3: Write the beta particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass # 97 Zr 40 97 e -1 Nb 41
Atomic #

17. electromagnetic γ no mass atomic always no omitted Gamma decay
Gamma rays – high-energy
radiation, denoted by the symbol
γ has no mass ( ) and no charge ( ). Thus, it causes change in or
numbers. Gamma rays almost accompany alpha and beta radiation. However, since there is effect on mass number or atomic number, they are usually from nuclear equations.
These can be shielded by lead or concrete. γ no
mass
atomic
always no
omitted

18. Type of Radioactive Decay
Review
Type of Radioactive Decay
Particle Emitted
Change in Mass #
Change in Atomic #
Alpha
α He -4 -2
Beta
β e +1
Gamma γ 4 2 -1