Periodic table
Videos
The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows and columns. An icon of chemistry, the periodic table is widely used
Liquid mercury. Its liquid state at standard conditions is the result of relativistic effects.
Graphite and diamond, two allotropes of carbon
Iron, a metal
Sulfur, a nonmetal
Hydrogen
Videos
Hydrogen is a chemical element; it has the symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under stand
Periodic table
…corresponds to a class of atom: these classes are called the chemical elements. The chemical elements are what the periodic table classifies and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on. Each of these names can be further abbreviated by a…
Purple glow in hydrogen's plasma state.
Robert Boyle, who discovered the reaction between iron filings and dilute acids
Antoine Lavoisier, who identified the element that came to be known as hydrogen
The Hindenburg over New York City in 1937