Graphene Graphene Graphene is an allotrope (form) of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice. It is a semimetal with small overlap between the valence and the conduction bands (zero bandgap material).<ref name="10.1002/adma.201502544 p.6519-6525"></ref> It is the basic structural element of many other allotropes of carbon, such as graphite, diamond, charcoal, carbon nanotubes and fullerenes. Graphene has many uncommon properties. It is the strongest material ever tested, conducts heat and electricity efficiently, and is nearly transparent. Graphene shows a large and nonlinear diamagnetism, greater than that of graphite, and can be levitated by neodymium
Two-electron atom Two-electron atom In atomic physics, a two-electron atom or helium-like ion is a quantum mechanical system consisting of one nucleus with a charge of "Ze" and just two electrons. This is the first case of many-electron systems where the Pauli exclusion principle plays a central role. It is an example of a three-body problem. The first few two-electron atoms are: The Schrödinger equation for any two-electron system, such as the neutral Helium atom (He, "Z" = 2), the negative Hydrogen ion (H, "Z" = 1), or the positive Lithium ion (Li, "Z" = 3) is: For a more rigorous mathematical