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 ...

The heaviest element that humans have ever found is called oganesson. Each atom of the stuff packs a whopping 118 protons into its dense center. In contrast, hydrogen—the most abundant element in the ...

At first glance, the system of chemical elements published by Dmitri Mendeleev in 1869 bears little resemblance to the modern periodic table. But by listing elements in columns, and lining up the ...