By the end of the 8th grade, students should know that all matter is made up of atoms, which are far too small to see directly through a microscope.
They should also understand that the atoms of any element are alike but are different from atoms of other elements.
Watch the video to see how and download the student handout (word document).
This lesson is the third in a three-part series about the nucleus, isotopes, and radioactive decay.
Other critics, perhaps more familiar with the data, question certain aspects of the quality of the fossil record and of its dating.