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Download Chapter 5: Electrons in Atoms
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Chapter 5: Electrons in Atoms Bohr’s Model •Niels Bohr •Changed Rutherford’s model because it lacked the ability to describe chemical properties. •Rutherford’s also did not account for atomic collapse. •Changed the model based upon how atoms absorb/emit light. •Hydrogen atom Bohr’s Contributions •Bohr discovered that electrons are not free, random-motion particles. •Major Contribution: •Electrons are found in circular paths, or orbits, around the nucleus. •Fixed Energy Bohr (cont.) •Energy levels are like rungs of a ladder. Energy Levels •Higher energy level = further from nucleus •Quantum → Move between energy levels. Energy Levels Bohr’s Ladder (Increasing Energy) 6th Level 5th Level 4th Level 3rd Level 2nd Level 1st Level •Energy levels are not equidistant. Electrons in Energy Levels •Degenerate vs. Excited Energy Levels • Electrons are lazy. • Emission of light. Energy → Lazy = Happy n=4 n=3 n=2 n=1 Flaws with the Bohr Model •Bohr’s Model: •Showed electrons in controlled orbits. (like planets) – often called “Planetary Model”. •Experiments greater than 1 electron systems failed to reproduce this motion. Oversights of Bohr •Electrons are not only moving around the nucleus but then are spinning as they move. •2 types of spin (more later) •Uncertainty of location of e- Heisenberg’s Uncertainty •Werner Heisenberg – you cannot know both the momentum and the location of an e-, you either know one or the other. •“Heisenberg’s Uncertainty Principle”
