Nuclear Chemistry Chapter 25

What do you think of when you hear Nuclear Chemistry?

History Henri Becquerel ( ) ◦Originally thought sunlight caused uranium to radiate ◦Discovered the spontaneous radiation while waiting for a sunny day to test his theory Marie Curie ( ) and her husband Pierre Curie ( ) ◦Worked w/ Becquerel ◦Eventually showed that the rays were from uranium atoms ◦Came up with the term “radioactivity” to describe Radiation – penetrating rays and particles emitted by a radioactive source.

Radiation An unstable nucleus releases energy by emitting radiation during the process of radioactive decay. What is an unstable nucleus? ◦Stability depends of the neutron to proton ratio. ◦Atoms with low atomic numbers (1-20) have a 1:1 ratio. ◦Above 20, stable nuclei have a 1.5:1 ratio. ◦Alpha Decay - Alpha Decay, Alpha Particles, Radioactivity - PhETAlpha Decay - Alpha Decay, Alpha Particles, Radioactivity - PhET

Types of Radiation Alpha Radiation- when a helium nuclei has been emitted from a radioactive source.

Types of Radiation Beta Radiation – An electron resulting from the breaking apart of a neutron in an atom.

Types of Radiation Gamma Radiation – a high-energy photon emitted by a radioisotope. (electromagnetic radiation) Extremely Dangerous!

Summary of Radiation ALPHA ◦Positive matter ◦Exactly like a Helium nucleus BETA ◦Negative matter ◦Exactly like an electron GAMMA ◦High energy wave ◦NOT matter so no charge

Types of Decay neutron to proton ratio determines the type of decay Four Types of Decay  Beta Decay  Electron Capture  Positron Emission  Alpha Decay

Beta Decay Too Many Neutrons! Beta Decay – neutron turned into a proton and electron 1 0 n 1 1 H + 0 e Example: 14 6 C 7 N+ 0 e

Electron Capture Too few neutrons! Electron Capture – convert proton to neutron; an e- is captured. Example: Ar + 0 e Cl

Positron Emission Positron – particle with the mass of an electron but a positive charge A proton changes to a neutron. Example: 8 5 B 8 4 Be e

Alpha Decay Too many neutrons and too many protons! Most common in atoms with an atomic number greater than 83. Alpha Emission – release of an alpha particle. Example: Ra Rn He

The blue ones have at least one stable isotope. Others do not!

Half-Life Half-life: is the time required for one half of the nuclei of a radio isotope sample to decay to stable products.