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Chemical Reactions. Involves the change of one or more substances into new substances Atoms are rearranged but their identities do NOT change The reaction involves the atom’s electrons only. Nuclear Reactions. An atom of one element changes into an atom of another element
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Chemical Reactions • Involves the change of one or more substances into new substances • Atoms are rearranged but their identities do NOT change • The reaction involves the atom’s electrons only
Nuclear Reactions • An atom of one element changes into an atom of another element • The identities of the atoms do change • Involves a change in the atom’s nucleus • Don’t occur that often in nature because many atoms have already decayed (undergone nuclear rxns) into stable atoms during Earth’s long history
Radioactivity • Some substances spontaneously emit radiation – it requires no energy • Occurs because an atom’s nucleus is unstable or overcrowded • The atom gains stability by losing energy or emitting radiation (like a pencil tipping over) • An atom continues to be radioactive and undergoes decay until its nucleus becomes stable
Radioactive Decay • 3 main types of radiation are emitted during radioactive decay (alpha, beta & gamma) – all 3 have energy & 1 has mass • The rays & particles emitted are known as RADIATION • The process of emitting them is radioactivity or radioactive decay
Nuclear Stability • The prime factor in achieving nuclear stability is for an atom to have a favorable neutron to proton ratio in its nucleus • Too high or too low leads to instability and nuclear decay
Alpha Radiation • Radiation made up of alpha particles • Each particle has 2 p+ and 2 no, so has a +2 charge and a mass of 4 amu • Basically a helium atom without electrons • The biggest and slowest of the three types, so it penetrates into matter the least
Beta Radiation • Consists of the fast moving electrons called beta particles • Has no mass but has a -1 charge • Smaller with more energy than alpha particles, so penetrate further • A beta particle breaks off of a neutron and leaves behind a proton
Gamma Radiation • It’s high energy radiation that has no mass, and no electrical charge • Highest energy of the 3, so penetrates the most & potentially the most damaging • Accounts for most of the energy lost during radioactive decay • Emission of gamma rays alone does not result in a new atom but usually accompanies beta & alpha radiation
Nuclear Equation • An equation that shows what happens during a nuclear reaction • Both the mass number and atomic number is conserved • Examples: Polonium-210 undergoes alpha decay
Nuclear Equation • Both the mass number and atomic number is conserved • Examples: Thorium-234 undergoes beta decay
Nuclear Equation • Both the mass number and atomic number is conserved • Examples: Uranium-234 undergoes alpha decay
Nuclear Equation • Both the mass number and atomic number is conserved • Examples: Bismuth-214 undergoes beta decay
Nuclear Equation • Both the mass number and atomic number is conserved • Examples: Uranium-238 undergoes alpha decay accompanied by 2 gamma rays
Did you know? • Radon exists only as a by-product of the radioactive decay of uranium-238. • Radon will further decay into radioactive isotopes of polonium, bismuth and lead. • All 3 of these isotopes are heavy metals that are difficult to remove from the human body. • It’s estimated 10,000 to 20,000 lung cancer deaths per year are caused by exposure to radon. • Radon is usually found in soil or building materials.
