Week One Wrap-Up
Module Review
In this module we began by discovering that the atom is composed of three particles: protons, neutrons, and electrons. Protons have a positive charge, electrons have a negative charge, and neutrons do not have a charge. After this, we learned about how to identify elements by the number of protons in the nucleus (Z; atomic number). We also learned to find the mass number (A), which is the total number of neutrons and protons in the nucleus of the atom (not listed within the periodic table).
We then left protons and neutrons behind to focus on the electron and learn about electromagnetic waves and their properties (wavelength, amplitude, frequency and interference pattern). Looking at the connection between wavelength and frequency, we learned from Planck that light behaves as waves and is made of streaming particles called photons.
We learned about our first understanding of electron structure of atoms by looking at Bohr's experiments with the emission spectra - obtained by energizing a sample of an element until it produces light and then passing that light through a slit and then a prism producing various wavelengths of light (some visible, some not). Bohr used the wavelengths produced (violet, blue-green, or red, for example) to determine that electrons can have only specific energy values. He proposed that photons corresponded with the movement of electrons (moving from outer 'orbits' to inner 'orbits').
We then discovered, with the help of de Broglie, that much like light, electrons also have a dual nature, being particles and behaving as waves. This proposal was proven by passing electrons through parallel slits onto a photosensitive paper. This experiment showed a diffraction pattern indicative of constructive and destructive interference of the waves that are bent after passing through the slits.
Last, we learned that it is impossible to design an experiment to observe an electron's wave nature and particle nature simultaneously. Heisenberg determined that the more we know about the position of an electron, the less we know about its velocity. We learned that electrons do not move as predictable orbits about the nucleus, but instead, due to Heisenberg's uncertainty principle, we can only define regions in space where we have a high probability of finding an electron.
Supplemental Material
If you would like to learn more on this topic, these resources may help:
The History of atomic Chemistry: Crash Course Chemistry
Completion Checklist
Make sure you complete the following learning activities and assessments before moving on to the next topic:
- Lecture Videos
- Example Videos (where posted)
- Practice Problems and Discussion
- Quiz