Nuclear Chemistry

Learning Targets I can describe the forces that hold the atom together I can explain why some isotopes are radioactive. I can describe the three types of radiation

Radiation Energy and/or particles are ejected from an unstable nucleus – Common sources of radiation Cosmic radiation – Sun – Exploding Stars Radioactive isotopes – Carbon-14 – Cobalt-60 – Plutonium-238

Radioactive Elements Elements with an unstable nucleus will spontaneously lose particles or energy to become stable – Instability is caused by an imbalance between protons and neutrons. The nucleus is held together with the STRONG FORCE, which at short distances is stronger than the electromagnetic force that would cause protons to repel At longer distances (larger nucleus) the electromagnetic force takes over and the nucleus begins to fall apart.

Radioactive Isotopes All elements with an atomic number over 83 are radioactive Many other smaller elements have radioactive isotopes. (Carbon-14) In graph (at right), shows the “Belt of Instability”. The dotted lines show the elements that are radioactive due to a unbalanced proton/neutron ratio

Types of Radiation Alpha radiation – A helium nucleus (2 protons and 2 neutrons) are ejected Beta radiation – A neutron becomes a proton, and an electron is ejected The nucleus changes! The atomic number is decreased by 2! The atomic number increases by 1!

Types of Radiation Gamma radiation – The nucleus does not change, but energy is released.