Decay product

In <a href="/facts/Nuclear_physics/fzQbt1aF">nuclear physics</a>, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining <a href="/facts/Nuclide/97Ykvzr3">nuclide</a> left over from <a href="/facts/Radioactive_decay/Ya6FVjt4">radioactive decay</a>. Radioactive decay often proceeds via a sequence of steps (<a href="/facts/Decay_chain/JvTwPNBn">decay chain</a>). For example, <a href="/facts/Uranium-238/QhcHm6q8">238U</a> decays to <a href="/facts/Thorium/ysdWH470">234Th</a> which decays to <a href="/facts/Isotopes_of_protactinium/AVGw4A8U">234mPa</a> which decays, and so on, to 206Pb (which is stable):

U
            
            
            
            
            238
          
          ⟶
        
        
          
            
              
                
                  
                    
                      
                        Th
                        
                        
                        
                        
                        234
                      
                      ⏟
                    
                  
                  
                    daughter
                     
                    of
                    
                       
                      
                        238
                      
                    
                    U
                  
                
                
                  ⟶
                
                
                  
                    
                      
                        Pa
                        
                        
                        
                        
                        
                          234
                          
                          
                          m
                        
                      
                      ⏟
                    
                  
                  
                    granddaughter
                     
                    of
                    
                       
                      
                        238
                      
                    
                    U
                  
                
                
                  ⟶
                  ⋯
                  ⟶
                  
                    
                      Pb
                      
                      
                      
                      
                      206
                    
                  
                
              
              ⏞
            
          
          
            decay
             
            products
             
            of
            
               
              
                238
              
            
            U
          
        
      
    
    {\displaystyle {\ce {^{238}U->}}\overbrace {\underbrace {\ce {^{234}Th}} _{\ce {daughter~of~^{238}U}}{\ce {->}}\underbrace {\ce {^{234\!m}Pa}} _{\ce {granddaughter~of~^{238}U}}{\ce {->\cdots ->{^{206}Pb}}}} ^{\ce {decay~products~of~^{238}U}}}

In this example:

<ul><li>234Th, 234mPa,...,206Pb are the decay products of 238U.</li>
<li>234Th is the daughter of the parent 238U.</li>
<li>234mPa (234 <a href="/facts/Nuclear_isomer/L8DHcqnk">metastable</a>) is the granddaughter of 238U.</li></ul>
These might also be referred to as the daughter products of 238U.
Decay products are important in understanding radioactive decay and the management of <a href="/facts/Radioactive_waste/MjYh5tlu">radioactive waste</a>.
For elements above <a href="/facts/Lead/EYljasJN">lead</a> in <a href="/facts/Atomic_number/bgAr581S">atomic number</a>, the decay chain typically ends with an <a href="/facts/Isotope/KD9B1y6o">isotope</a> of lead or <a href="/facts/Bismuth/75FLjkoX">bismuth</a>. Bismuth itself decays to <a href="/facts/Thallium/v35pGMJB">thallium</a>, but the decay is so slow as to be practically negligible.
In many cases, individual members of the decay chain are as radioactive as the parent, but far smaller in volume/mass. Thus, although uranium is not dangerously radioactive when pure, some pieces of naturally occurring <a href="/facts/Uraninite/EsEwMErJ">pitchblende</a> are quite dangerous owing to their <a href="/facts/Radium-226/T0SlGtRH">radium-226</a> content, which is soluble and not a ceramic like the parent. Similarly, <a href="/facts/Thorium/ysdWH470">thorium</a> <a href="/facts/Gas_mantle/d56ATf6b">gas mantles</a> are very slightly radioactive when new, but become more radioactive after only a few months of storage as the daughters of 232Th build up.
Although it cannot be predicted whether any given atom of a radioactive substance will decay at any given time, the decay products of a radioactive substance are extremely predictable. Because of this, decay products are important to scientists in many fields who need to know the quantity or type of the parent product. Such studies are done to measure pollution levels (in and around nuclear facilities) and for other matters.

Decay product open-in-new

Decay product