Discover the history, structure, and importance of the periodic table of elements, from Mendeleev’s discovery to modern scientific applications. When you purchase through links on our site, we may ...

RUN your fingers over the white keys of a piano. The notes get higher and higher as your hand moves to the right. On the eighth key, something beautiful happens: a note hangs in the air that embodies ...

Note: This video is designed to help the teacher better understand the lesson and is NOT intended to be shown to students. It includes observations and conclusions that students are meant to make on ...