Glossary

GLOSSARY

• Activity
  Radioactivity is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. The total number of decays per unit time is called activity.
  
  
• Atomic number Z
  The atomic number or proton number (Z) is the number of protons of a nucleus. The atomic number uniquely identifies a chemical element.
  
  
• Becquerel
  Becquerel (Bq) is the unit of measure of activity defined by the International System of Units (SI), named in honor of the scientist Henri Becquerel. 1 Bq is defined as 1 decay per second.
  
  
• Curie
  Curie (Ci) is a further unit of measure of activity, not belonging to the International System of Units, but still used in some contexts, named in honor of the scientist Marie Skłodowska Curie. 1 Ci is equal to $3.7x10^{10}$ Bq and corresponds to the activity of one gram of Radium.
  
  
• Decay constant
  The decay constant (symbol: λ and unit of measure: $8^{-1}$) of a radioactive nuclide is its probability of decay per unit time.
  
  
• Half-life
  The half-life is the time required for the number of radioactive nuclei present at the initial instant to be halved.
  
  
• Isotopes
  Isotopes are nuclei having same atomic number Z but different mass number A.
  
  
• Mass number A
  The mass number (A) is defined as the sum of the number of protons and neutrons of a nucleus.