Abundance of the chemical elements stars. Lithium, beryllium and boron are rare because although they are produced by nuclear fusion, they are then destroyed by other reactions in the stars. The elements from carbon to iron are relatively more common in the universe because of the ease of making them in supernova nucleosynthesis. Elements of higher atomic number than iron (element 26) become progressively more rare in the universe, because they increasingly absorb stellar energy in being produced. Elements with even atomic numbers are generally more common than their neighbors in the periodic table, also due to favorable energetics of formation. The abundance of elements
Periodic table of topological invariants dimensions can be labeled by the elements of the formula_46-th homotopy group of the symmetric space. These groups are displayed in this table, called the periodic table of topological insulators: There may also exist weak topological invariants (associated to the fact that the suspension of the Brillouin zone is in fact equivalent to a formula_66 sphere wedged with lower-dimensional spheres), which are not included in this table. Furthermore, the table assumes the limit of an infinite number of bands, i.e. involves formula_67 Hamiltonians for formula_68. The table also is periodic in the sense that the group of invariants in formula_46