The Importance of Neutrons
1)  Neutrons :  can't build the elements without them
 §    the strong nuclear force holds nuclei together even though protons repel each other
 §    it works like velcro : only unlike particles can stick
Result : the elements have almost equal numbers of protons & neutrons
 
      Example:  Deuterium burning
         (this is very quick and easy)
2)  Neutrons fall apart by themselves after about 10 minutes!
 §    you can make them by squeezing electrons into protons
at high density
§    they are held by the weak nuclear force, which makes them pretty stable in nuclei
§    sometimes they decay even in nuclei (beta decay)
P
P
P
P
N
N
+
He3
H2
H1