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Half Lifes. 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
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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