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Unit 2: The Atom. Nuclear Decay. Band Of Stability. Atoms that lie outside the band of stability are unstable Atoms 1-20 n 0 /p + ratio must be 1:1 Atoms 21-83 n 0 /p + ratio is ~ 1.5 : 1 Atoms 84 and up are ALL unstable.
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Unit 2: The Atom Nuclear Decay
Band Of Stability • Atoms that lie outside the band of stability are unstable • Atoms 1-20 n0/p+ ratio must be 1:1 • Atoms 21-83 n0/p+ ratio is ~ 1.5 : 1 • Atoms 84 and up are ALL unstable • Unstable atoms will lose pieces of itself until it becomes stable. – This is Nuclear Decay
3 Types of Decay Region A: Atoms have too many neutrons; Beta Decay Region B: Atoms have too many protons;Positron emission and e- capture Region C: Elements have too many neutrons and protons; Alpha Decay
I am an isotope that have too many neutrons and protons… What to do? Alpha decay!!! Atoms that undergo alpha decay lose 2 protons and 2 neutrons α (alpha particles)are simply the nucleus of a He atom with no electrons!!) The result is an atom with loweratomic number and mass Alpha Decay
Alpha Decay • Alpha decay is how elements greater than atomic #83 try to become stable. • They will emit an alpha particle (2 neutrons and 2 protons) to try to become stable. • Alpha reactions will always have He on the right side! • To balance: write the upper and lower equations! 210 = 206 + 4 84 = 82 + 2
Beta Decay • I am an isotope with too many neutrons… what to do? • Get rid of a neutron by Beta Decay! • During Beta decay, a neutronis converted into a proton and e-(which is ejected from the nucleus) Neutron = proton + electron • Beta particles are known as high energy electrons • The extra proton creates an atom with a higher atomic number There are 2 ways to write a Beta particle!
Beta Decay 14 = 14 + 0 • Beta decay is how elements who have too many neutrons try to become stable (on top of the band) • Beta reactions will always have ß or e-on the right side! 6 = 7 + -1
Gamma Decay • Gamma decaynever happens alone! (it usually accompanies alpha or beta decay) • It represents a photon of energy or light • Gamma decay alone involves no transformation or change of an atom’s nucleus
Gamma Decay 233 = 229 + 4 + 0 93 = 91 + 2 + 0 The * represents extra energy that will be lost.
Practice For each of the following, fill in the missing parts of the equation: 131 Rn
Nuclear Decay Series • Radioactive atoms will continue to decay until they reach a stable nucleus. • For large atoms with atomic number greater than 83, the stable element will be lead.
Detecting Radiation • Radioactive particles can be detected by a Geiger Counter which gives a clicking sound for each particle detected. • Different types of radiation required different types of protection. • The greater the distance from a radioactive source will give better protection.
Radiation Safety Alpha Particles • Cannot penetrate very far into matter. • Cannot penetrate a sheet of paper. • Cannot penetrate your skin. • Only dangerous to humans if eaten or inhaled.
Beta Particles • Can penetrate a bit more deeply • Can be stopped by a sheet of aluminum foil or plexiglass. • Only dangerous to people if eaten or inhaled.
Gamma Particles • The most penetrating (have the most energy). • They will penetrate the body through the skin and do damage. • Have more energy than an x-ray • Can only be stopped by thick pieces of lead
