The Neutron

The Neutron is an elementary particle found in the nucleus of the atom with the proton.  Its neutral charge is caused by the quark composition (udd or up, down, down) because the charges of the quarks add (up=2/3 + down=-1/3 + down=-1/3 = 0) to zero.  Bound inside the nucleus neutrons are stable, but the free neutron (synthetic) is unstable, having a half-life of about 885 seconds (approx. 15 minutes).  It interacts with all four forces and through beta decay, it becomes a proton.  The neutron is the heaviest particle in the atom.