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Timeline. Day 7. Overview. We’ve gone through several theories and contributions recently Thomson’s plum pudding Millikan’s experiment Rutherford’s experiment Bohr model Its time to summarize and see how they all connect. Defending and critiquing the theories. - PowerPoint PPT Presentation
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Timeline
Day 7
Overview
• We’ve gone through several theories and contributions recently– Thomson’s plum pudding– Millikan’s experiment – Rutherford’s experiment– Bohr model
• Its time to summarize and see how they all connect
Defending and critiquing the theories
• You will represent one of the four scientists • Point out the problems with the previous
scientists theories • Outline “your” contribution or model with
your group• We will critique Bohr together as a class
• Thomson – Plum Pudding– Why? Known that negative charges can be
removed from atom.– Problem: just a random guess
• Rutherford – Solar System– Why? Scattering showed hard core.– Problem: no good explanation for electron
movement
• Bohr – fixed energy levels– Why? Explains spectrum, includes quantization– Problem: electrons should spiral into nucleusPhet.colorado.edu
Models of the Atom
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Problems with the Bohr Model
• The electrons are traveling in a circle- this means they are accelerating (why?)
• Accelerating charges give off radiation- thus they lose energy
• Electrons in Bohr’s orbitals would actually spiral into the nucleus
• Inherent in all of Bohr’s postulates is the idea that electrons are like tiny planets- this is not the case
If electron’s aren’t tiny planets, what are they?
• Similar to nucleus, electron charge discoveries- based on experiments
• Different because these upcoming theories changed the way people think about matter
The approach
• We are going to examine the nature of light in order to understand the electron
• Don’t confuse light and electrons- they are different entities
• We will eventually see that they are very similar however!
• Next time: We will see that light behaves as a wave. And it behaves as a stream of particles.