03 Notes - Isotopes

03 Notes - Isotopes - How can we use this info to calculate...

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Pluchino – Regents Chemistry Atoms, Formuals & Reactions – 03 Isotopes Aim: What are isotopes? Do Now: If there are always a whole number of protons and neutrons in an atom, why are the masses of atoms rarely a whole number? Isotopes: atoms of an element that have the same number of protons, but different number of neutrons. Isotopes will have different atomic masses , but the same atomic number . Practice: Calculate the number of neutrons in each isotope. 1. K-39, K-41 2. Br-79, Br-81 3. Cu-63, Cu-65 Isotopic Abundance: relative percentage of the isotopes of an element. Cl-35 occurs in 75.8% of all Cl atoms Cl-37 occurs in 24.2% of all Cl atoms
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Unformatted text preview: How can we use this info to calculate the average atomic mass of an element? 35 amu x 0.758 = 28.5 amu + 37 amu x 0.242 = 8.95 amu 35.45 amu Practice: Calculate the average atomic mass of each element. 1. K-39 (93.2%), K-41 (6.80%) 2. Rb-85 (72.17%), Rb-87 (27.83%) Challenge: Calculate the isotopic abundance of each isotope. Cu-63 Cu-65 Average atomic mass = 63.456 amu Conclusions: Isotopes of an atom have different numbers of neutrons Isotopes of the same element have the same number of protons. Use isotopic abundance and mass information to determine average atomic mass...
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This note was uploaded on 01/01/2012 for the course CHEM 101 taught by Professor Donahue during the Spring '11 term at Long Island U..

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