Site provides extensive information in the study of comets. Includes excellent graphics that depict what comets look like as they travel through the solar system. Also includes information on how comets may have effected the Earth's...

This site provides an illustrated and animated story that seeks to answer several questions. What are atoms made of? What is keeping a nucleus intact? What happens if you try to separate two quarks? Are quarks fundamental?

[Free Registration/Login may be required to access all resource tools.] The nucleus is only found in eukaryotic cells. It contains most of the genetic material of the cell. It is surrounded by a double membrane, or nuclear envelope, that...

Activity 3 of this module investigates: How do we know what's inside an atom? From Ernest Rutherford's Gold Foil Experiment to his investigation of the Plum Pudding model, students become aware of the Nuclear Model of an Atom. Also in...

[Free Registration/Login may be required to access all resource tools.] Humans are in the same domain as trees and algae. What could they possibly have in common? It is the location of their DNA inside their cells. Their cells all have a...

[Free Registration/Login may be required to access all resource tools.] What a radioisotope is and why they have unstable nuclei. Elements in which all of the isotopes are radioactive.

This site from the encyclopedia Wikipedia provides a basic definition for what the atomic radius is, and an explanation of what covalent and metallic radii are.