Interactive, scaffolded model
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First, students experiment with how orbital shapes are affected by other charges and atoms. Then, students explore the role of electronegativity in bond formation by setting the electronegativities of two bonded atoms. They should see that ionic bonds form between atoms of very disparate electronegativities, and that polar covalent bonds form between atoms of somewhat disparate electronegativities, and non-polar covalent bonds form between atoms that have similar electronegativities. Finally, they will also see how a molecular surface becomes polarized when polar covalent bonds are part of a larger molecule.
Students will be able to:
The intention of this activity is that it would be run over two separate class days, so that the students would complete Part 1, then have a class discussion, perhaps revisiting some of the key models together via an LCD projector or smart board, and then complete Part 2 the next day. Having students complete the entire computer based activity in one sitting is not recommended.
Prerequisite: Because students explore the formation of chemical bonds using atoms that depict electrons in orbitals instead of orbits, it would be helpful if they had some understanding of basic atomic structure and concept of a simple orbital. There are also several representations of molecules in this activity, so understanding that molecules can be visualized in various ways, yet still be the same molecule, will also be a benefit.
The last part of the activity connects the idea of polarity to the properties of various amino acids. While not necessary, if the students were already familiar with the idea that a protein is linked chain of amino acids, it would be beneficial.
The type of bond formed -- ionic, non-polar covalent, or polar covalent -- depends on the electronegativity of the two atoms that are bonded together.
Additional Related Concepts
Fermi Lab's ARISE project recommends the following as extensions to this SAM activity:
By understanding the different types of bonds that can form, many physical properties can be understood, including boiling point and solubility.
Last Update: 11/25/2008
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