NUCLEAR CHEMISTRY

Introduction to Nuclear Chemistry  Nuclear chemistry is the study of the structure of and the they undergo.

Chemical vs. Nuclear Reactions Chemical ReactionsNuclear Reactions Occur when bonds are brokenOccur 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 electronsMay involve protons, neutrons, and electrons Associated with small energy changesAssociated with large energy changes Reaction rate influenced by temperature, particle size, concentration, etc. Reaction rate is not influenced by temperature, particle size, concentration, etc.

Alpha radiation  Composition – Alpha particles, same as helium nuclei  Symbol – Helium nuclei, He, α  Charge – 2+  Mass (amu) – 4  Approximate energy – 5 MeV  Penetrating power – low (0.05 mm body tissue)  Shielding – paper, clothing 4 2

Beta radiation  Composition – Beta particles, same as an electron  Symbol – e -, β  Charge – 1-  Mass (amu) – 1/1837 (practically 0)  Approximate energy – 0.05 – 1 MeV  Penetrating power – moderate (4 mm body tissue)  Shielding – metal foil

Gamma radiation  Composition – High-energy electromagnetic radiation  Symbol – γ  Charge – 0  Mass (amu) – 0  Approximate energy – 1 MeV  Penetrating power – high (penetrates body easily)  Shielding – lead, concrete

Chemical Symbols  A chemical symbol looks like…  To find the number of, subtract the from the C 6 14

Alpha Decay  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 2.  Alpha decay causes the number to decrease by and the number to decrease by.  determines the element. All nuclear equations are. 4 2

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

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

Beta decay  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.  Beta decay causes change in number and causes the number to increase by. 0 -1

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

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

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.

Transmutation  – the of one atom of one element to an atom of a different element ( decay is one way that this occurs!)

Review Type of Radioactive Decay Particle Emitted Change in Mass # Change in Atomic # Alpha α He -4-2 Beta β e 0+1 Gamma γ

Nuclear Reactions  Characteristics:  Isotopes of one element are into isotopes of another element  Contents of the change  amounts of are released

Types of Nuclear Reactions  decay – alpha and beta particles and gamma ray emission  Nuclear - emission of a or

Nuclear Fission  - of a nucleus  - Very heavy nucleus is split into approximately fragments  - reaction releases several neutrons which more nuclei  - If controlled, energy is released (like in ) Reaction control depends on reducing the of the neutrons (increases the reaction rate) and extra neutrons ( creases the reaction rate).

Nuclear Fission  - 1 st controlled nuclear reaction in December st uncontrolled nuclear explosion occurred July  - Examples – atomic bomb, current nuclear power plants

Nuclear Fusion  - of a nuclei  - Two nuclei combine to form a heavier nucleus  - Does not occur under standard conditions ( repels )  - Advantages compared to fission -,  - Disadvantages - requires amount of energy to, difficult to  - Examples – energy output of stars, hydrogen bomb, future nuclear power plants