Topic 2: Basic Shape Recognition
Searching the database using the "shapes" search
option is a great way to have students learn to recognize the basic molecular
shapes.
There are a lot of shapes to choose from if the entire
database is being used, so if you want to make sure that students are only
looking at basic shapes for the time being (a.k.a. in a very introductory
course) I suggest using the "entry level" data base which only
includes simple diatomic, linear, bent, trigonal planar, trigonal pyramidal and
tetrahedral molecules.
Suggested activity #1
You could have students do an exploration on their own to
become familiar with the shapes (click "entry level" at the top, and
then "select all" and “view” to see a list of molecules that fit the
criteria. If you want to narrow down the shapes search, search by shape and
then go back to the periodic table to deselect any atoms you do not want to
have included in your search or if you have particular molecules in mind for
them to look at do a text search for the name or formula of the compound. )This site is especially good for students to get a clear picture of the
molecular shapes because they can explore at home, click and drag the molecules
into all types of positions so they can see symmetry and understand the 3d
nature of molecules without having to make models for all of the shapes. They
can also get a feel for the approximate angles between atoms that are
associated with the various shapes if students are asked to make some kind of
table associating bond angles with the molecular shape.
We suggest exploring the database yourself first and then
possibly picking out some of the structures you especially like to show the
class or to ask the students to look at in particular. A projection of the
rotatable structures make the structures come to life during a lecture, and can
be used to supplement the models most teachers use to introduce basic molecular
shapes.
Suggested activity #2
Students can use the pdf files which are the Molecular
Origami patterns for the molecule to make a physical model at home or in the
classroom. No matter how good the digital technology is, sometimes there is
simply no substitute for having a touchable 3-dimensional model.
Suggested activity #3
A fun activity to make sure students are really
comfortable with the basic shapes is to have them look at larger molecules and
identify all the basic shapes that make up that molecule. (sort of a “Where’s
Waldo?” activity) Click here to see
the molecules we have found that would work well for this activity.
