In 1869, Mendeleev's first periodic table did not include them, as closed-shell elements remained undiscovered until Lord Rayleigh and William Ramsey isolated argon in 1894. Remarkably ...

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. Elements in ...

The South Atlantic Anomaly represents a region within near-Earth space characterized by a significantly weaker geomagnetic ...

As we move down the column of Group 7 elements, their reactivity decreases. In each, the outer shell is further from the nucleus and the incoming electron is not as easily attracted to it.