BETA DECAY

When a neutron ceases to exist in a nucleus, a proton and electron are created (together with a tiny, uncharged and almost undetectable relative of the electron called an antineutrino).  The electron is shot out of the nucleus at high speed.  The proton has now replaced the neutron, increasing the proton number by 1.

Iodine-131 decays by a beta particle emission, forming a xenon-131.

131 53

I

-->

0 -2

b +

131 54

Xe

+ energy