Radioactive
Decay means that a particle is lost or in other words a
particle is produced. In algebra x - 1 = y can be
rewritten as x = y + 1. In chemistry we use the
same
properties
to write a chemical equation. If Iodine-131 produces
(loses) a beta particle to produce xenon-131. The
equation could be written as 
,
but
since
we do not write equations with negatives, we rearrange it
algebraically to get 
.
Keep
in mind that all chemical equations are written without the
use of negatives, regardless of what occurs in the reaction.
Alpha Decay
In alpha decay, an atom will produce an alpha
particle. When you write a nuclear equation, mass must
be conserved. The total mass on the left of the arrow,
and the total mass on the right of the arrow are
equal. In addition to mass being conserved, the total
number of protons on the left must equal the total number of
protons on the right.
Radium-222 undergoes alpha decay to produce
radon-218.
The total mass on the left is 222 and the total mass on
the right is 222 (4 + 218). The total number of
protons on the left is 88 and the total number of protons on
the right is 88 (2 + 86).
During alpha decay, the mass of the parent atom decreases
by 4 and the atomic number decreases by 2.
Beta Decay
In beta decay, an atom will produce a beta particle
(electron). Please keep in mind that this is different
from losing an electron to become an ion. In beta
decay a neutron becomes a proton by producing an
electron. When an atom loses an electron to become an
ion, the atom is simply losing an electron from outside the
nucleus. Thorium-234 will become protactinium-234 by
producing a beta particle.
During beta decay, the mass does not change but the
atomic number increases by 1.
Gamma Rays
Electromagnetic radiation, with a short wavelength, and very
high energy. Produced by the rearrangement of particles in
the nucleus or certain electron transitions. Very
penetrating, very dangerous.
Positron Decay
In positron decay, an atom will produce a particle that
has the same mass as an electron but with a positive
charge. Sodium-22 will undergo positron emission to
produce neon-22.
During positron decay, the mass does not change but the
atomic number decreases by 1.
