Unit #1Unit #2Unit #3Unit #4Unit #5Unit #6Unit #7Unit #8Unit #9Unit #10
spacerUNIT # 3  

spacerof the Atom

spacerAtomic Number - Number of Protons
spacerNumber of Electrons
spacerMass Number - Number of Neutrons
spacer3.2 Isotopes
spacer3.3 Arrangement
spacerof Electrons

spacerThe Bohr Model
spacerBohr Diagram
spacerThe Lewis Electron-dot Symbol
spacerThe Quantum Mechanical Model of the Atom
spacerElectrons in the sublevels

spacer3.4 Electron

spacerFilling Order of the Sublevels

spacerElectron Configuration Notations
spacerElectron Configuration for Atoms of the First 20 Elements
spacerElectron Configuration and the Periodic Table
spacer3.5 Atomic Mass
spacerCalculation of Atomic Mass
spacerCalculate the Atomic Mass of Carbon

spacer1 | 2 | 3

Unit # 3 - Atomic Structure
Calculations of atomic mass
  1. The three stable isotopes of silicon have masses and natural abundances as follows. Calculate the atomic mass.

    28Si 27.976927 amu 92.23%
    29Si 28.976495 amu 4.67%
    30Si 29.973770 amu 3.10%
  2. There are two stable isotopes of bromine. Isotope A has a mass of 78.918336 amu and isotope B has a mass of 80.916289 amu.
    • Determine the natural abundance of the isotopes, and report the answer to three significant figures.

    • Write the symbol for the two isotopes.
  3. There are two naturally occurring isotopes of silver, 107Ag and 109Ag. The atomic mass of silver is 107.87 amu, with 51.82% of the atoms being 107Ag. The mass of an atom of 107Ag is 106.9 amu. What is the mass, in amu, of an atom of 109Ag.


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