NOTES

Radioactivity

It is the radiation of unstable nuclei as they decay. A Geiger counter can be used to detect and measure radioactivity.

Alpha Decay

Example

238               4           234

      U     -->     He   +       Th

  92               2             90

Beta Decay

During beta decay one neutron decomposes into one proton and one electron.

1             0         1

  n    -->    e   +    p

0            -1         1

The proton is added to the atomic number and mass, and the electron is emitted. Therefore, the number of protons increases.

Example

234                0         234

      Th     -->     e   +       Pa

  90               -1           91

Positron Emissions

During positron emission one proton changes into a neutron and a positron.

  1              0          1

    p   -->      e   +     n

  1            +1          0

The neutron is added to the mass, and the positron is emitted. Therefore, the number of protons decreases.

Example

30               0         30

    P     -->     e   +       Si

15               1          14

Gamma Decay

When nuclei decay, they remains in high energy states until they release gamma radiation to achieve a more stable state.

Electron capture

During electron capture the nucleus captures a low energy electron (electrons close to the nucleus). This electron is combined with one proton to form one neutron.

  0         1          1

    e   +    p -->    n

 -1         1          0

The neutron is added to the mass and the number of protons decreases.

Example

18              0            18

     F      +     e  -->       O

   9            -1              8   

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