Radioactive Decay

6.1  Radioactive Decay
 
  Radioactivity  
 

A spontaneous process where an unstable nucleus changes into a more stable nucleus by emitting radiations.

 
     
 
  Radioactive radiation  
 

The release of high-energy particles.

 
     
 
 

The characteristics of the radioactive radiation:

  1. Ionizing power
    • \(\alpha\) highest, \(\gamma\) lowest
  2. Penetrating power
    • \(\alpha\) lowest, \(\gamma\) highest
  3. Can be stopped by
  4. In electric field
  5. In magnetic field
 
 
  Decay of nuclei  
 

The process by which unstable nuclei emit radioactive rays to be more stable nuclei.

Spontaneous: the decay rate is not controlled, happens by itself, not affected by the chemical composition or physical factors (temperature, pressure, light, electric and magnetic fields)

 
     
 
 
  Alpha decay  
 

\(^A _Z X \space \rightarrow ^{A-4} _{Z-2} Y + ^4 _2 \text He\)

where,

\(^{A-4} _{Z-2} Y\) is the new element and,

\(^{4} _2 \text He\) is the alpha particle.

 
     
 
  Beta decay  
 

\(^A _Z X \space \rightarrow \space ^A _{Z+1} R+ ^0 _{-1} \beta\)

where,

\(^{A} _{Z+1} R\) is the new element and,

\(^{0} _{-1} \beta\) is the beta particle.

 
     
 
  Gamma decay  
 

\(^A _Z \text X \rightarrow ^A _Z \text X + T\)

When a radioisotope emits a gamma-ray, it does not change the value of the nucleon number (\(A\)) or the value of the proton number (\(Z\)).

No new element will be created when a nucleus emits a gamma-ray.

 
     
 
 
  Half-life  
 

The time taken by a radioactive sample to decay by half of its original mass.

 
     
 

The concept of half-life can be described as follows:

 

The half-life value can be determined from the graph of the activity against time or the graph of the number of atoms, N radioactive against time: