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Radioactivity and Nuclear Energy Chapter 19

Importance of the Nucleus Chemical properties are determined by the number and arrangement of electrons Chemical properties are determined by the number and arrangement of electrons Nucleus does NOT strongly affect the behavior of an atom Nucleus does NOT strongly affect the behavior of an atom BUT the nucleus is very important BUT the nucleus is very important

Uses of nucleus Detecting explosives in luggage Detecting explosives in luggage Generation of electric power Generation of electric power Determining the ages ancient items Determining the ages ancient items All these use nuclear processes All these use nuclear processes

Facts about the Nucleus Size Size Very small Very small Radius typically cm Radius typically cm 1/100,000 the size of a typical atom 1/100,000 the size of a typical atom If the nucleus of a H atom were the size of a ping pong ball, its electron would be about 0.5km (0.3) miles away If the nucleus of a H atom were the size of a ping pong ball, its electron would be about 0.5km (0.3) miles away

Facts about the Nucleus Density Density 1.6 x g/cm x g/cm 3 If the nucleus were the size of a ping pong ball, it would have a mass of 2.5 billion tons If the nucleus were the size of a ping pong ball, it would have a mass of 2.5 billion tons

Facts about the Nucleus Energy Energy Nucleus held together very well Nucleus held together very well Energy in nuclear processes typically millions of times larger than normal chemical reactions Energy in nuclear processes typically millions of times larger than normal chemical reactions

Facts about the Nucleus Composed of nucleons: neutrons and protons Composed of nucleons: neutrons and protons Number of protons is atomic number (Z) Number of protons is atomic number (Z) –Located at the lower left of element Sum of the numbers of neutrons and protons is mass number (A) Sum of the numbers of neutrons and protons is mass number (A) –Located at the upper left of element

Nuclide Symbol P = ?N = ?Mass # ? Atomic # ?

Isotopes and Nuclides Isotopes: atoms that have identical atomic numbers but different mass numbers Isotopes: atoms that have identical atomic numbers but different mass numbers Nuclide: general term applied to each unique atom Nuclide: general term applied to each unique atom

Isotopes and Nuclides Example: the following nuclides are considered isotopes of each other Example: the following nuclides are considered isotopes of each other Carbon-12, carbon-13, and carbon-14 Carbon-12, carbon-13, and carbon-14 All have six protons (Z=6), and they have 6, 7, and 8 neutrons All have six protons (Z=6), and they have 6, 7, and 8 neutrons

Radioactivity EMR – energy that has wave-like behavior and travels at the speed of light EMR – energy that has wave-like behavior and travels at the speed of light Radioactivity – the result of the spontaneous decomposition of a nucleus. This may include high energy EMR and high energy particles Radioactivity – the result of the spontaneous decomposition of a nucleus. This may include high energy EMR and high energy particles

Radioactive Isotopes 85% of the 2000 known isotopes are radioactive. 85% of the 2000 known isotopes are radioactive. 279 are not radioactive 279 are not radioactive % abundance is much, much smaller. % abundance is much, much smaller. C-12 – 99% of all C C-12 – 99% of all C C-14 < 0.1% C-14 < 0.1%