Monday, October 20, 2014

An Alien Periodic Table

The story of Mendeleev is one that most chemistry teachers tell.  He is commonly considered the father of the Periodic Table.  A video I used to show referred to him as "a bearded Russian who liked to play cards."  He laid out cards with element properties, looked for patterns, predicted properties of unknown elements.  Hearing all that doesn't exactly make him exciting to kids.  Putting them in his shoes is another story.

I have just wrapped up my unit on atomic structure and the periodic table.  For years now, my colleagues and I have been using an alien periodic table as a common lab experience to help kids understand the magnitude of Mendeleev's work and the reference that hangs on our wall.  I had used some type of "alien periodic table" - give kids some pretend elements with pretend properties and ask them to arrange them - for years, but I really like the one we use now because it asks them to work in stages, each one with more information than the previous.  I like how this forces them to iterate an idea several times to come up with one that grows, even over just 45 minutes of class.

We start with information about element color, melting point, and hardness - all easy properties to observe - and ask for a first arrangement.  Then we add information about reactivity.  Make some changes to accommodate the new information while trying to maintain the original organizational structure.  We finish with adding mass to the known data and ask them to tweak and polish it up.  The next day we follow with an arrangement that mirrors our own table and ask them to use it to predict.  The results are often very good.

Here are three sample student papers:

I love how they all start in similar but not identical ways, but by Stage 2, they are settling on almost identical structures.  This is a great place to talk about how there may be many different ways to organize information, but often a way or two emerge as the best ways.  Of course, I tell them that there doesn't have to be a right way.  If they can justify their system, it's a good way.  I evaluate their work based on how well their tables evolve over the course of the activity.  Did they try to incorporate all the data?  Can I see growth from Stage 1 to Stage 3?  At the end, though, they all usually settle on something pretty similar to other groups.

I love this activity for so many reasons.  It's great to see them really try to make sense of and organize data.  It's a cool way to show them what scientists like Moseley and Mendeleev were doing.  And to give them a sense of how risky and pioneering new scientific ideas can be.  If you don't already so a "create a periodic table" activity, do a quick Google search and find one that you might try.  Kids like the puzzle nature of it and rise to the challenge.  As inquiry activities go, it's low risk - kids won't hurt themselves with element cards.  If you do one, want to share it?  Feel free to do so in the comments.

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