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Unit cell of sodium peroxide Na 2 O 2. The sodium ions are violet and the peroxide ions in red. In chemistry, metal peroxides are metal-containing compounds with ionically- or covalently-bonded peroxide (O 2− 2) groups. This large family of compounds can be divided into ionic and covalent peroxide.
This table lists only the occurrences in compounds and complexes, not pure elements in their standard state or allotropes. Noble gas +1 Bold values are main oxidation states
For each atom, the column marked 1 is the first ionization energy to ionize the neutral atom, the column marked 2 is the second ionization energy to remove a second electron from the +1 ion, the column marked 3 is the third ionization energy to remove a third electron from the +2 ion, and so on.
Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion.
Applied to molecular ions, this algorithm considers the actual location of the formal (ionic) charge, as drawn in the Lewis structure. As an example, summing bond orders in the ammonium cation yields −4 at the nitrogen of formal charge +1, with the two numbers adding to the oxidation state of −3:
The peroxide group is marked in blue. R, R 1 and R 2 mark hydrocarbon moieties. The most common peroxide is hydrogen peroxide (H 2 O 2), colloquially known simply as "peroxide". It is marketed as solutions in water at various concentrations. Many organic peroxides are known as well. In addition to hydrogen peroxide, some other major classes of ...
For reasons of space, [30] [31] the periodic table is commonly presented with the f-block elements cut out and positioned as a distinct part below the main body. [32] [30] [23] This reduces the number of element columns from 32 to 18. [30] Both forms represent the same periodic table. [6]
Like the periodic table, the list below organizes the elements by the number of protons in their atoms; it can also be organized by other properties, such as atomic weight, density, and electronegativity. For more detailed information about the origins of element names, see List of chemical element name etymologies.