The number of protons in the nucleus of the atom, I believe.  c:
        
             
        
        
        
Cs -137 has a half life of about 30 years. If 60 years pass, there is two half lives passed so 1/2 * 1/2= 1/4. Take 1/4 and multiply it with the mass given:
(1/4)*20mg=5mg left
        
             
        
        
        
Answer:
Based on safety and carbon emissions, fossil fuels are the dirtiest and most dangerous, while nuclear and modern renewable energy sources are vastly safer and cleaner.
 
        
             
        
        
        
Answer:
http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/imgbio/treecycle.p ng
Explanation:
 
        
             
        
        
        
Answer:
Yes N3- is correct ion notation. The N element is in the form N2 . Also it is a triple covalent bond and so this correct