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This article explores the fundamentals of atomic structure, focusing on protons, neutrons, and electrons while introducing the concept of half-lives. It explains how the atomic number determines the identity of elements, exemplified by hydrogen and uranium. The discussion includes isotopes, highlighting the role of neutrons, and details radioactive decay types such as alpha and beta decay. A practical example using carbon-14 showcases the half-life concept and its application in determining the age of organic materials, emphasizing the predictable nature of atomic decay.
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Atoms • Proton • Electron Cloud • Neutron
Atomic Number • Number of protons – change this → change the element • Hydrogen has one proton and one electron • Atomic number = 1 • Uranium has 92 of each • Atomic number …
Isotopes! • Have to deal with number of neutrons in the nucleus • For the most part Hydrogen atoms have no neutrons but… • Deuterium has one neutron in the nucleus • 1/6,000 Hydrogen atoms is Deuterium
Atomic Mass Number • Neutral but do add mass to the nucleus • The atomic mass number indicates the total number of protons and neutrons in the nucleus • Carbon 14 (6 protons and 8 neutrons)
Radioactive Decay • Unstable Nuclei sometimes decay • Types of decay • Alpha Decay, Beta Decay, Electron Capture • Uranium-238 – alpha decay ejects a helium nucleus leaving Thorium -234 • Atomic number is changed – new element
Radioactive Decay • Carbon-14 (6 protons, 8 neutrons) decays by emitting an electron when neutron → proton • Daughter isotope has 7 protons and 7 Neutrons • Nitrogen-14 • Beta Decay
Half life • Atoms can decay in a predictable way • The time it would take for half of the atoms of a sample to decay
Half life example • Suppose we find a rock with a mass of 100 grams that is entirely carbon-14 • Carbon 14 decays to Nitrogen 14 with a half life of 5730 years • This means that after this amount of time our rock will contain 50 grams of carbon 14 and 50 grams of Nitrogen 14 • After an additional 5730 years we’ll have 25 grams of carbon 14 and 75 grams of Nitrogen 14