Chlorine naturally exists as two isotopes, \(_{17}^{35}\textrm{Cl}\) (chlorine-35) and \(_{17}^{37}\textrm{Cl}\) (chlorine-37). The abundance of chlorine-35 is 75% ...

This video is an interactive lesson in calculating an atom’s mass and atomic number. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells. The numbers of ...

Standard atomic weights, those numbers emblazoned under the elements on the periodic table, were once thought of as unchanging constants of nature. But researchers have tweaked the atomic weights of ...

For the first time those little numbers that appear beneath some of the commonest elements in the periodic table boxes are about to change from a single value to an interval of numbers An ...

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 ...

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 ...

Standard atomic weights, those numbers emblazoned under the elements on the periodic table, were once thought of as unchanging constants of nature. But researchers have tweaked the atomic weights of ...