Nuclear Chemistry

  • Chemical Symbol:

    • Mass number - atomic number = neutron number

  • Chemical vs. Nuclear Reactions

Chemical Reactions

Nuclear Reactions

Occur when bonds are broken

Occur when nuclei emit particles or rays.

Atoms are unchanged, but can be rearranged

Atoms usually converted into different elements

Involve valence electrons only

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 not influenced by temperature, particle size, concentration, etc.

  • Nuclear Fission

    • Splitting of a nucleus

    • Chain reaction, one particle sets off another atom

    • Nuclear reactors control these situations, allowing energy to be released slowly.

  • Nuclear Fusion

    • Combines nuclei

    • Does not normally happen because protons repel each other

    • Inexpensive, does not produce radioactive waste, but is unrealistic power source as of now because requires lots of energy and very hard to control.

    • Examples: Stars, hydrogen bomb

  • Nuclear stability

    • Very stable - Atomic numbers 1-20 tend to have 1:1 ratio of protons to neutrons

    • Marginally stable - Atomic numbers 21-82 tend to have 1:1.5 ratio of protons to neutrons.

    • Unstable/radioactive - Atomic number >82 tend to have >1:1.5 ratio of protons to neutrons

    • Strong force keeps nucleus together despite proton repulsion

    • If there are too many neutrons strong force will fail, and release particles out of the nucleus.

  • Types of Decay

    • Alpha Decay - Unstable nucleus emits a particle composed of 2 protons and 2 neutrons (helium nuclei). They have a charge of 2+ because there are no electrons. Can be written out with helium symbol and the mass and atomic number or with alpha alpha symbol.

    • Beta Decay: Neutrons converted into protons, and electrons (β particles) shown as (β or e-). Have -1 charge.

    • Gamma Emissions:

      • High energy released

      • Particles are not lost from nucleus

      • Usually occurs after nucleus goes through decay and remaining particles rearrange. No charge on gamma emissions, just energy

      • Electron Capture: nucleus captures low energy electron

        • usually occurs when mass number less than normal

      • Positron emission: like beta emission but with a positive charge.

        • usually occurs when mass number less than normal

  • Decay can take multiple steps in a decay series.