Discover the history, structure, and importance of the periodic table of elements, from Mendeleev’s discovery to modern scientific applications.

This article explains how to find valence electrons using group numbers and electron configurations, provides examples of valence electrons in different elements, and explores their role in ...

This video excerpt from NOVA's "Hunting the Elements" explains why some elements are more reactive than others.

The number of protons in an atom is referred to as the atomic number of that element. The number of protons also determines the chemical behavior of the element.

Electrons generally orbit atomic nuclei in distinct shells, but calculations show that the outer electrons of oganesson, the heaviest element found so far, may instead orbit the nucleus as a gas.