p7 radioactivity

• When an atom has lost electrons it becomes a positive ion
• An isotope is an atom that has the same number of protons but different number of neutrons
• A radioscope emits ionising radiation
• Background radiation comes from artificial or natural sources
• Natural sources of background radiation are food, rocks
• Artificial sources of background radiation are x-rays, fallout from nuclear power stations
• ‘Plum pudding model’ was discovered by JJ Thompson It was a positive sphere with negative electrons randomly scattered throughout
• when a radio scope emits alpha particles the nucleus looses two protons and tw/o neutrons
• When a radioscope emits a beta particle the nucleus looses one neutron and gains one proton
• When a radioscope emits a gamma wave the nucleus doesn’t change
• Gamma waves are emitted after alpha or beta for sure energy is conserved
• Radioactivity is a random process so it is not possible predict which nucleus will decay next
• The half life is the time taken for the number of nuclei to decay by half
• Contamination happens when there is radioactive material outside your body
• Irradiation happens when you take radioactive material inside your body or on your skin
• Induced fission produces 2-3 neutrons, 2 smaller nuclei and gamma rays
• Induced fission is when a slow moving neutron hits a large nucleus
• Spontaneous fission is very rare and happens naturally without a neutron being absorbed
• In a steady state reactor one fission neutron from each fission event will go on to produce more fission
• The nuclear model of the atom was made after the Rutherford scattering experiment that showed an atom has a small dense positively charged nucleus
• The Bohr-Rutherford model of the atom was made when Niels Bohr suggested the electrons orbited the nucleus at specific distances
• Nuclear fusion is the  of two  nuclei to make a single  nucleus. When this occurs, a lot of  is emitted in the form of electromagnetic radiation.