Nuclear ChemistryNuclear Chemistry

The study of nuclear reactions and The study of nuclear reactions and their use in chemistrytheir use in chemistry

Basic DefinitionsBasic Definitions

Nucleons - particles that reside in the nucleus Nucleons - particles that reside in the nucleus – protons and neutrons– protons and neutrons

Isotopes – atoms of an element with the same Isotopes – atoms of an element with the same number of protons but different numbers of number of protons but different numbers of neutronsneutrons

Mass Number – sum of p+ and nMass Number – sum of p+ and n00. . Atomic Number – number of p+ and e- in a Atomic Number – number of p+ and e- in a

neutral atom neutral atom

A Brief History A Brief History In 1896, Henri Becquerel expanded the field of chemistry to In 1896, Henri Becquerel expanded the field of chemistry to

include nuclear changes when he discovered that uranium include nuclear changes when he discovered that uranium emitted radiation.  Soon after Becquerel's discovery, Marie emitted radiation.  Soon after Becquerel's discovery, Marie Sklodowska Curie began studying radioactivity and completed Sklodowska Curie began studying radioactivity and completed much of the pioneering work on nuclear changes.  Curie found much of the pioneering work on nuclear changes.  Curie found that radiation was proportional to the amount of radioactive that radiation was proportional to the amount of radioactive elementelement present, and she proposed that radiation was a present, and she proposed that radiation was a property of property of atomsatoms (as opposed to a chemical property of a (as opposed to a chemical property of a compoundcompound).  Marie Curie was the first woman to win a Nobel ).  Marie Curie was the first woman to win a Nobel prize and the first person to win two (the first, shared with her prize and the first person to win two (the first, shared with her husband Pierre and Becquerel for discovering radioactivity; husband Pierre and Becquerel for discovering radioactivity; the second for discovering the radioactive the second for discovering the radioactive elementselements radium radium and polonium). and polonium).

Marie CurieMarie Curie

Radiation – wave Radiation – wave energy from any power energy from any power sourcesource

Radioactivity – energy Radioactivity – energy emitted from decaying emitted from decaying atomsatoms

Stability of AtomsStability of Atoms

Most atoms are stableMost atoms are stable Certain nuclides are unstable because of the Certain nuclides are unstable because of the

size of the atom or the ratio of protons and size of the atom or the ratio of protons and neutrons in the nucleineutrons in the nuclei

Radioisotopes – are atoms of an element that Radioisotopes – are atoms of an element that produce nuclear radiation ( they are produce nuclear radiation ( they are radioactive ).radioactive ).

Types of Nuclear RadiationTypes of Nuclear Radiation

Alpha Radiation (a)Alpha Radiation (a) An a particle contains 2 An a particle contains 2 protonsprotons and 2 and 2 neutronsneutrons

(and is similar to a He nucleus: ). (and is similar to a He nucleus: ). When an When an atomatom emits an a particle, the atom's emits an a particle, the atom's

atomic massatomic mass will decrease by 4 will decrease by 4 unitsunits (because (because 2 2 protonsprotons and 2 and 2 neutronsneutrons are lost) and the are lost) and the atomic numberatomic number (z) will decrease by 2 (z) will decrease by 2 unitsunits.  . 

The The elementelement is said to 'transmute' into another is said to 'transmute' into another elementelement that is 2 z units smaller.  that is 2 z units smaller. 

An example of an a transmutation takes place An example of an a transmutation takes place when uranium decays into the element thorium when uranium decays into the element thorium (Th) by emitting an alpha particle as depicted (Th) by emitting an alpha particle as depicted in the following equation:in the following equation: 238 234 4 238 234 4

U ----> Th + HeU ----> Th + He

92 90 2 92 90 2