Do you like to build things?  How about blocks or toys or a chair that comes out of the box in parts?  When you build something bigger out of smaller parts, it can become useful.  It can do something more together than each of its parts could do when they were apart.  What was a pile of bricks is now a house to keep someone safe.  What was a bunch of plastic pieces are now a lamp to light the room.  This is true on a very, very small scale too.  Atoms are the small things that come together to make molecules which make up everything.  The same atoms can be used in different ways to build different kinds of molecules.  How would you like to build a molecule, the things that make the world what it is?  You would?  Good.  Let's open our ammonia building kit.


Today we are going to build an ammonia molecule.  Ammonia is a gas that does not have any color and kind of smells like cat pee.  So why would we want to make the stuff?  Well when put in water it makes a great cleaner.  It also makes it so that soil, can grow more crops over and over in the same place.  Finally, it's a simple molecule.  Trust me, when you are building the world, you want to start simple.

I don't think cat pee smells so bad.


Now let's open the little plastic bags that hold our pieces.  Ammonia is made of only two parts.  We will make the base first.  Nitrogen is a gas with no color that makes up 78% of the air around the Earth!  From now on, we will just call it N.  When building our molecule, you can think of this N as the base.  It's the big metal circle the lamp will stand on.  It's the flat piece of plastic that the LEGOs will be built upon.  It's the chain from which the light will hang.  Right now, let's put the N in the middle of where we are going to build.  It may be helpful to draw this as you might building instructions.


Now let's tear open this little bag with the smaller pieces inside.  Like I said, ammonia is only made of two parts.  We have our N, which is the base, and now we have these three smaller pieces that will connect to it.  Hydrogen is the most common element in the universe and we can find it in our Sun, making heat and light for us.  From now on, we will just call it H.  Like N, this gas has no color.  Unlike N, the gas H has no smell or taste.  You may remember H from that other molecules you might have built, like H2O.  Water.  H's are found everywhere.  They are like the little screws that are in everything you have built.

That's a lot of hydrogen atoms. We won't need all these to build ammonia.


We have all of our pieces!  Now what?  As you can see, these four pieces can fit together in many different ways: a line, a circle, a square . . . and on and on.  Of course, if you build a couch upside down, then no one will be able to sit on it.  Each kind of molecule must come in one shape.  A Lewis Structure is a diagram we use to show the ways that different atoms are connected in a molecule.  You can make one now.  Write an N in the middle of a sheet of paper.  Great.  Now use the three H's to make a T shape, with the N at the point where the horizontal and vertical lines cross.  Now connect them with lines.

It should look like this:

H--------N--------H
             I
             I
             I
            H

Told you this was easy.


Now get ready to stretch your brain a little bit.  What you see above is just the 2-D model of an ammonia molecule.  We need to think of it in 3-D.  What good would a couch be if it just laid flat as a piece of paper on the floor?  It needs to fill space!  It may be a little hard to think about, but the ammonia molecule is in the shape of a pyramid.  When it comes to molecules, pyramidal means that one atom sits above, while the others are down below, like a base.  Think of N as the top of a pyramid with the three H's as the bottom corners.  If it helps, find a ball of one color (this will be the N) and three smaller balls of another color (these will be the H's).  Set the three smaller balls in a triangle on your desk and then hold the N above the middle of the triangle.  See it now?

A Nitrogen playing dog pile on Hydrogen atoms.


Sweet!  You just built your first molecule!  You took all of the smaller pieces, atoms and put them together.  You set the base, N, and then from above made a T shape with your three H's to make a Lewis Structure.  Then you made it 3-D by lifting the N up in the air to make a pyramidal shape.  Pieces did not fly everywhere.  You did not have to break anything, or return it to the shop . . .  I cannot say the same thing will happen the next time you need to build something from IKEA.


References:


Ducksters.  "Hydrogen"  Ducksters, 2010.  <http://www.ducksters.com/science/chemistry/hydrogen.php>

Science Daily.  "Lewis Structure in Chemistry"  Science Daily, 2014.  <http://www.sciencedaily.com/articles/l/lewis_structure.htm>