Glad you asked...
Oxygen atom models aren't very hard to make at all. Using a different color for the electrons, protons and neutrons will make your model visually appealing. You will need craft paints and several other things for this activity. Check out this site for more information on making an oxygen model: http://www.ehow.com/how_5692356_construc...
Then again, this answer might help you...
Glue about 12 Styrofoam balls together to make your nucleus. Then take small sticks with Styrofoam balls to make your protons. Place your nucleus on a piece of cardboard or construction paper and then place any electrons around the nucleus as if it were circling the sun.

