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Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium. [68] About 0.9% of the Sun 's mass is oxygen. [ 19 ] Oxygen constitutes 49.2% of the Earth's crust by mass [ 69 ] as part of oxide compounds such as silicon dioxide and is the most abundant element by mass in the Earth's crust .
Singlet oxygen is the common name used for the two metastable states of molecular oxygen (O 2) with higher energy than the ground state triplet oxygen. Because of the differences in their electron shells, singlet oxygen has different chemical and physical properties than triplet oxygen, including absorbing and emitting light at different ...
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). [1] Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of organic heterocycles. [2]
3, form when oxygen combines with other elements. Due to its electronegativity, oxygen forms chemical bonds with almost all other free elements at elevated temperatures to give corresponding oxides. However, some elements, such as iron which oxidises to iron oxide, or rust, Fe 2 O 3, readily oxidise at standard conditions for temperature and ...
In chemistry and biology, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (O 2), water, and hydrogen peroxide. Some prominent ROS are hydroperoxide (H 2 O 2 ), superoxide (O 2 − ), [ 1 ] hydroxyl radical (OH .
Tetraoxygen was first predicted in 1924 by Gilbert N. Lewis, who proposed it as an explanation for the failure of liquid oxygen to obey Curie's law. [1] Though not entirely inaccurate, computer simulations indicate that although there are no stable O 4 molecules in liquid oxygen, O 2 molecules do tend to associate in pairs with antiparallel spins, forming transient O 4 units. [2]
Perhaps red for oxygen is inspired by the fact that oxygen is normally required for combustion or that the oxygen-bearing chemical in blood, hemoglobin, is bright red, and the blue for nitrogen by the fact that nitrogen is the main component of Earth's atmosphere, which appears to human eyes as being colored sky blue. [6] [better source needed]
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8, meaning each oxygen atom has 8 protons in its nucleus.