Oxidation of elemental metals by oxygen (commonly known as rusting, which is similar to tarnishing):
Compounds of oxygen
Soil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors.
Until the late 1960s, soil chemistry focused primarily on chemical reactions in the soil that contribute to pedogenesis or that affect plant growth. Since then, concerns have grown about environmental pollution, organic and inorganic soil contamination and potential ecological health and environmental health risks. Consequently, the emphasis in soil chemistry has shifted from pedology and agricultural soil science to an emphasis on environmental soil science.
The oxidation state of oxygen is −2 in almost all known compounds of oxygen. The oxidation state −1 is found in a few compounds such as peroxides. Compounds containing oxygen in other oxidation states are very uncommon: −1⁄2 (superoxides), −1⁄3 (ozonides), 0 (elemental, hypofluorous acid), +1⁄2 (dioxygenyl), +1 (dioxygen difluoride), and +2 (oxygen difluoride).
Oxygen forms compounds with almost all of the other known elements, including some of the rarest: technetium (−
4TcO), promethium (Pm
3), neptunium (NpO
2), plutonium (PuO
2), americium (AmO
2), curium (CmO
2), berkelium (BkO
2) and californium (Cf
3); and also with some of the least reactive elements such as xenon (XeO
3), gold (Au
3) and platinum (PtO
2). Synthetic elements that have known oxides include einsteinium (Es
3). The few elements that oxygen will not react with in typical conditions are the noble gases helium, neon, argon and krypton.
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Elements are divided into metals, metalloids, and non-metals. Familiar examples of elements include carbon, oxygen (non-metals), silicon, arsenic (metalloids), aluminium, iron, copper, gold, mercury, and lead (metals).
The lightest chemical elements, including hydrogen, helium (and smaller amounts of lithium, beryllium and boron), are thought to have been produced by various cosmic processes during the Big Bang and cosmic-ray spallation. Production of heavier elements, from carbon to the very heaviest elements, proceeded by stellar nucleosynthesis, and these were made available for later solar system and planetary formation by planetary nebulae and supernovae, which blast these elements into space. The high abundance of oxygen, silicon, and iron on Earth reflects their common production in such stars, after the lighter gaseous elements and their compounds have been subtracted. While most elements are generally viewed as stable, a small amount of natural transformation of one element to another also occurs at the present time through decay of radioactive elements as well as other natural nuclear processes.