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Oxygen is the most abundant element in Earth's crust, and the third-most abundant element in the universe after hydrogen and helium. At standard temperature and pressure, two oxygen atoms will bind covalently to form dioxygen, a colorless and odorless diatomic gas with the chemical formula O 2.
Elements with low electronegativities, such as most metals, easily donate electrons and oxidize – they are reducing agents. On the contrary, many oxides or ions with high oxidation numbers of their non-oxygen atoms, such as H 2 O 2, MnO − 4, CrO 3, Cr 2 O 2− 7, or OsO 4, can gain one or two extra electrons and are strong oxidizing agents.
These effects usually combine to give heat capacities lower than 3R per mole of atoms in the solid, although in molecular solids, heat capacities calculated per mole of molecules in molecular solids may be more than 3R. For example, the heat capacity of water ice at the melting point is about 4.6R per mole of molecules, but only 1.5R per mole ...
A representation of Hess's law (where H represents enthalpy) Hess's law of constant heat summation, also known simply as Hess's law, is a relationship in physical chemistry and thermodynamics [1] named after Germain Hess, a Swiss-born Russian chemist and physician who published it in 1840.
In thermodynamics, the enthalpy of mixing (also heat of mixing and excess enthalpy) is the enthalpy liberated or absorbed from a substance upon mixing. [1] When a substance or compound is combined with any other substance or compound, the enthalpy of mixing is the consequence of the new interactions between the two substances or compounds. [ 1 ]
Covalent and ionic bonding form a continuum, with ionic character increasing with increasing difference in the electronegativity of the participating atoms. Covalent bonding corresponds to sharing of a pair of electrons between two atoms of essentially equal electronegativity (for example, C–C and C–H bonds in aliphatic hydrocarbons).
Fusion takes place when atoms come into close proximity and the nuclear force pulls their nuclei together to form a single larger nucleus. Counteracting this process is the positive charge of the nuclei, which repel each other due to the electrostatic force. For fusion to occur, the nuclei must have enough energy to overcome this coulomb barrier.
2 has an overall charge of −1, so each of its two equivalent oxygen atoms is assigned an oxidation state of − 1 / 2 . This ion can be described as a resonance hybrid of two Lewis structures, where each oxygen has an oxidation state of 0 in one structure and −1 in the other. For the cyclopentadienyl anion C 5 H −