Elements in group 1 and group 2 are metals. Atoms of group 1 elements have one electron in their outer shell, and atoms of group 2 elements have two electrons in their outer shell. Some elements in ...

Early periodic tables were incomplete, since many elements were unknown. Also, some elements were placed in groups with elements that were not similar to them. Mendeleev left gaps for elements not ...

This year we celebrate the 150th anniversary of one of the most significant breakthroughs in science, the creation of a tool that allows us to make sense of the basic ingredients of our universe, and ...