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Basic particle descriptions

Basic particle descriptions. atom – the fundamental unit of which elements are composed (neutral: p + = e - ; n 0 varies) ion – atom that has lost or gained electrons and carries a charge ( p + ≠ e - ; n 0 same)

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Basic particle descriptions

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  1. Basic particle descriptions • atom – the fundamental unit of which elements are composed (neutral: p+ = e-; n0 varies) • ion – atom that has lost or gained electrons and carries a charge (p+ ≠ e-; n0 same) • isotope – atoms of the same element that have different numbers of neutrons (protons equal, but neutrons unequal)

  2. Further clarification • An isotope refers to a group of atoms within each element with a specific mass number. • Every atom is an isotope. • Isotopes are referred to by their mass number; eg. carbon-12 or uranium-238

  3. Measurement with Mass Spectrometer Diagram Instrument

  4. amu – atomic mass unit • 1 amu = 1/12 of a carbon-12 atom • Approximately = 1 proton or neutron • Approximately = 1.66 x 10-27 kg • amu is useful on an atomic scale, but we will use units in class that are equivalent and more meaningful to the sizes we handle: grams/mol (g/mol)

  5. Calculating atomic mass(weighted average) • Turn each percentage into a decimal number. • Multiply each mass by its matching decimal number. • Add them.

  6. Problem 1 – Atomic mass bromine Bromine has two isotopes with the first having a mass of 78.91 amu and occupying 50.69% and the second isotope having a mass of 80.91 amu and occupying 49.31%. What is the average atomic mass of bromine? 0.5069(78.91 amu) + 0.4931(80.91 amu) = 79.90 amu = 79.90 g/mol

  7. Problem 2 – Atomic mass Verify the atomic mass of chlorine using this data for its two isotopes: chlorine-35 = 34.96 amu; percent abundance = 75.77% chlorine-37 = 36.96 amu percent abundance = 24.23% 0.7577(34.96 amu) + 0.2423(36.96 amu) = 35.44 amu = 35.44 g/mol

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