p9 - Nuclear Reactions Alpha, Beta, and Gamma Decay CS 4.2...

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Unformatted text preview: Nuclear Reactions Alpha, Beta, and Gamma Decay CS 4.2 State what is meant by alpha, beta and gamma decay of radionuclides. CS 4.3 Identify the processes occurring in nuclear reactions written in symbolic form. The Atom The atom consists of two parts: 1. The nucleus which contains: protons neutrons 2. Orbiting electrons. The Atom All matter is made up of elements (e.g. carbon, hydrogen, etc.). The smallest part of an element is called an atom. Atom of different elements contain different numbers of protons. The mass of an atom is almost entirely due to the number of protons and neutrons. Mass number = number of protons + number of neutrons A X Z Element symbol Atomic number = number of protons X Z A Z = number of protons + number of neutrons = number of protons A A – Z = number of neutrons Number of neutrons = Mass Number – Atomic Number There are many types of uranium: 235 A Z U 92 238 A Z U 92 Number of protons Number of neutrons Number of protons Number of neutrons There are many types of uranium: 235 A Z U 92 235 92 92 143 238 A Z U 92 238 92 92 146 Number of protons Number of neutrons Number of protons Number of neutrons Isotopes of any particular element contain the same number of protons, but different numbers of neutrons. Most of the isotopes which occur naturally are stable. A few naturally occurring isotopes and all of the manmade isotopes are unstable. Unstable isotopes can become stable by releasing different types of particles. This process is called radioactive decay and the elements which undergo this process are called radioisotopes/radionuclides. Radioactive Decay Radioactive decay results in the emission of either: • an alpha particle (α), • a beta particle (β ), • or a gamma ray(γ ). Alpha Decay An alpha particle is identical to that of a helium nucleus. It contains two protons and two neutrons. Alpha Decay A X Z A-4 Y + 2 He Z-2 alpha particle 4 unstable atom more stable atom Alpha Decay 222 226 Ra 88 Rn 86 4 He 2 Alpha Decay A X Z A-4 Y+ Z-2 222 4 He 2 4 226 Ra 88 Rn + 86 He 2 Alpha Decay 222 Rn 86 Rn 86 A Y + 2 He Z 4 4 222 218 Po + 84 He 2 Alpha Decay A X Z U 92 230 Th + 2 He 90 Th + 2 He He 90 4 4 234 230 Alpha Decay 230 Th 90 Th 90 Y + 2 He Z 226 A 4 230 Ra + 2 He 88 4 Alpha Decay A X Z 218 214 Pb + 2 He 82 Pb + 2 He 82 4 4 Po 84 214 Beta Decay A beta particle is a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay. Beta decay occurs when a neutron changes into a proton and an electron. Beta Decay As a result of beta decay, the nucleus has one less neutron, but one extra proton. The atomic number, Z, increases by 1 and the mass number, A, stays the same. Beta Decay 218 218 Po 84 At 85 β -1 0 Beta Decay A X Z Y + -1β Z+1 218 A 0 218 Po 84 Rn + 85 β -1 0 Beta Decay 234 Th 90 Th 90 A Y + -1β Z Pa + 91 β -1 0 0 234 234 Beta Decay A X Z 210 Pb + -1β 82 Pb + 82 β -1 0 0 210 Tl 81 210 Beta Decay 210 Bi 83 Bi 83 A Y + -1β Z Po + 84 β -1 0 0 210 210 Beta Decay A X Z 214 Bi + -1β 83 Bi + 83 β -1 0 0 214 Pb 82 214 Gamma Decay Gamma rays are not charged particles like α and β particles. Gamma rays are electromagnetic radiation with high frequency. When atoms decay by emitting α or β particles to form a new atom, the nuclei of the new atom formed may still have too much energy to be completely stable. This excess energy is emitted as gamma rays (gamma ray photons have energies of ~ 1 x 10-12 J). ...
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p9 - Nuclear Reactions Alpha, Beta, and Gamma Decay CS 4.2...

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