Measuring Radioactivity

• Curies measure an atom's rate of decay.Stockbyte/Stockbyte/Getty Images
  
  Radioactivity is the amount of ionizing radiation given off by an atom. Material is emitted from the atom in the form of alpha and beta particles, gamma rays and neutrons. X-rays also are ionizing radiation. Ionization means the particles or energy emitted is enough to remove electrons from surrounding atoms. The units for measuring the decay are curie (Ci) and becquerel (Bq).
  
  

What Is a Curie

• A single curie is equivalent to 37 billion becquerels.Thinkstock/Comstock/Getty Images
  
  Radiation is the disintegration of atoms, and is measured in disintegrations per second. The International System of units (SI) measures radioactivity in becquerel (Bq) and it represents one disintegration per second. The common unit for measuring radioactivity is the curie (Ci), and it represents 37 billion disintegrations per second. A millicurie is 37 million and a microcurie is 37,000 disintegrations per second.
  
  

Exposure, Absorbed Dose and Dose Equivalent

• Marie Curie died of leukemia after years of exposure to radioactivity.Photos.com/Photos.com/Getty Images
  
  The rate of decay is just one method for determining the amount of radioactivity; exposure, absorbed dose and dose equivalent also measure it. Exposure is the amount of radioactivity traveling through the air, and is measured in roentgen (R) or coulomb/kilogram (C/kg). Absorbed dose represents the amount of radiation absorbed by the body. The units for this are radiation absorbed dose (rads), and the SI units are gray (Gy). The dose equivalent takes into account the absorbed dose and the physiological effects. The dose equivalent depends on the area of exposure and the strength of the radioactive source.
  
  

Marie and Pierre Curie

• Marie and Pierre Curie are best known for their research with radioactive chemicals.Photos.com/Photos.com/Getty Images
  
  Marie and Pierre Curie studied and worked in Paris. In 1903, they won half the Nobel Prize in Physics for their work in radioactivity. Henri Becquerel won the other half. Marie won a second Nobel Prize in 1911 for chemistry. Pierre did not share the prize, because he died in April 1906. He was run over by a carriage on a Paris street. The Curies discovered two radioactive elements: polonium and radium. Marie also improved the process for purifying radium from ore.