Go back to Natural Types of Radioactivity
This is a method of showing the precise changes that happen to a nucleus during a nuclear change.
During a nuclear change, total mass number and total atomic number are conserved.
α decay
eg.
Note that on both sides of the second equation
the total mass number is 218 and the total atomic number is 84.
Note also; the Po is called the parent
while the Pb is called the daughter.
More on alpha decay
β decay
or 
γ decay . These take place in company after either alpha or beta from the new nucleus as it stabilises to a lower internal energy level. When gamma is emitted, neither atomic nor mass numbers change.
The "m" next to the 24 indicates that the nucleus is not yet at its most stable, it is "excited". The term used is "metastable". After the initial decay, the nucleus has not yet reverted to its most stable form so the gamma is emitted bringing the nucleus to its least energetic value. (Sometimes a star is used instead of the m.)
The total reaction leading to this result would be described by;
Practice on the U-238
decay chain.
ACTIVITY OF RADIOACTIVE MATERIALS
Near a counter, different samples of materials will produce differing count rates. These count rates are a measure of the ACTIVITY of the material. Active samples make the counter spin, inactive samples don't.
ACTIVITY = number of disintegrations each second
The activity is measured in becquerels, Bq.
Count Rate represents a fraction of the activity because of
