Radioactive Decay

nuclear instability:  If the nucleus of an atom is unstable, the strong nuclear force is unable to hold it together, and a piece of it splits off.  When the piece splits off, the nucleus ends up with a different number of protons, which means the atom literally turns into an atom of a different element.

Nuclei can become unstable if:

· they are too large (more than 82 protons)

· there are too many or too few neutrons for the number of protons in the nucleus

band of stability:  isotopes with a ratio of protons to neutrons that results in a stable nucleus (one that does not spontaneously undergo radioactive decay).

radioactive decay:  the process by which a nucleus loses matter, which transforms the element into a different element or isotope.

nuclear equation:  an equation describing (through chemical symbols) what happens to an atom as it undergoes radioactive decay.

alpha (α) decay:  a type of radioactive decay in which the nucleus loses two protons and two neutrons (an alpha particle).  An alpha particle is identical to the nucleus of a  atom.  For example:

beta minus (β−) decay:  a type of radioactive decay in which the nucleus loses a high speed electron.  In this process, a neutron is changed into a proton, so the atomic number increases by one, but the mass number stays the same.  Also, an electron is ejected from the nucleus.  In nuclear equations, an electron is given the chemical symbol .  For example:

gamma (γ) rays:  most radioactive decay produces a lot of energy.  Some of that energy is emitted in the form of gamma rays.  Gamma rays are a high energy form of light that can do a lot of damage.  Because gamma rays are not particles, emission of gamma rays does not change the composition of the nucleus.