RADIATION *Penetrating rays emitted by a radioactive source *Ranges from Cosmic and Gamma Rays to Radio Waves

RADIOACTIVE DECAY *Unstable atoms have excess internal energy. *the nucleus can undergo a spontaneous change towards a more stable form.

3 types of RADIATION α – radiation (alpha radiation) – radiation ß – radiation (beta radiation) γ – radiation (gamma radiation)

α – decay: *Emission of an α – particle *Particle is a Helium nucleus *Element changes to a new element – a Transmutation occurs 42 Heα or 4242

α – decay equation Atomic mass decreases by 4 Atomic number decreases by U Th He

α – decay Ra Rn He

α – decay *Particle carries a positive charge *Large, heavy particle - moves slowly *Little penetrating power *stopped by skin or a sheet of paper

ß -decay ß - decay *Emission of a beta - particle *Particle is an electron *A transmutation occurs - a neutron changes into a proton and an electron 0e or o ß

ß -decay equation ß - decay equation *Atomic mass stays the same *Atomic number increases by C o e 14 7 N +

ß -decay ß - decay

*Particle carries a negative charge *Small, light-weight particle * fast-moving *Penetrates 1-2 cm of skin or water *can be stopped by metal sheet a few mm thick

γ – radiation Emission of electromagnetic energy from an atom’s nucleus No particles are emitted A transmutation does not occur

γ – radiation  Identical to X-rays  Energy transmitted in waves  Great penetrating power - can pass through human body

γ – radiation *Thick barriers of lead, concrete, or water are used as protection against them

Graph of unstable nuclei Too many neutrons Tend to beta decay Too many protons and neutrons Tend to alpha decay Too many protons Capture e - to convert p + to n 0

Many radioactive elements have to go through a series of decays to reach a stable isotope

Detecting Radiation Radiation is ionizing radiation – it knocks electrons off of the substances it hits to produce ions Instruments can detect this process

Detecting Radiation Geiger counter – uses gas to detect radiation. Ionized gas particles conduct electricity and produce audible clicks

Detecting Radiation Scintillation counter - uses phosphor to detect radiation Phosphors produce flashes of light when hit by ionizing radiation

Detecting Radiation Film badge – uses photographic film to detect radiation Worn by personnel working near radiation sources to monitor exposure

Half – life The Half-life is the time it takes for half of the atoms of a radioactive substance to decay. After one half-life the level of radioactivity of a substance is halved, after two half-lives it is reduced to one quarter, and so on

Half-life Graph

Fission Fission is a nuclear process in which a heavy nucleus splits into two smaller nuclei after being bombarded with neutrons n U U Ba 91 36Kr 1010n n 1010 n

Fission Reaction

Fission reactions Controlled fission is used in Nuclear Reactors to produce useful energy

Fusion Fusion occurs when two nuclei combine to produce a nucleus with a heavier mass 2121 H H 4242 He n + energy

Fusion Reaction Fusion Fusion reactions reactions release more release more energy then energy then fission reactions fission reactions