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  2. Hydrogenation - Wikipedia

    en.wikipedia.org/wiki/Hydrogenation

    Hydrogenation is a chemical reaction between molecular hydrogen (H 2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule ...

  3. Hydrogen cycle - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_cycle

    The hydrogen cycle consists of hydrogen exchanges between biotic (living) and abiotic (non-living) sources and sinks of hydrogen-containing compounds. Hydrogen (H) is the most abundant element in the universe. [1] On Earth, common H-containing inorganic molecules include water (H 2 O), hydrogen gas (H 2), hydrogen sulfide (H 2 S), and ammonia ...

  4. Dissociation (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Dissociation_(chemistry)

    For instance, when an acid dissolves in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton (H +) and a negative ion. Dissociation is the opposite of association or recombination .

  5. Hydrogen compounds - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_compounds

    Hydrogen compounds are compounds containing the element hydrogen. In these compounds, hydrogen can form in the +1 and -1 oxidation states. Hydrogen can form compounds both ionically and in covalent substances. It is a part of many organic compounds such as hydrocarbons as well as water and other organic substances.

  6. Hydrogen - Wikipedia

    en.wikipedia.org/wiki/Hydrogen

    Hydrogen forms compounds with less electronegative elements, such as metals and main group elements. In these compounds, hydrogen takes on a partial negative charge. The term "hydride" suggests that the H atom has acquired a negative or anionic character, denoted H −. Usually hydride refers to hydrogen in a compound with a more ...

  7. Protonation - Wikipedia

    en.wikipedia.org/wiki/Protonation

    In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), usually denoted by H +, to an atom, molecule, or ion, forming a conjugate acid. [1] (The complementary process, when a proton is removed from a Brønsted–Lowry acid, is deprotonation.) Some examples include The protonation of water by ...

  8. Chemical reaction - Wikipedia

    en.wikipedia.org/wiki/Chemical_reaction

    A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. [1] When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an energy change as new products are generated.

  9. Chemical bond - Wikipedia

    en.wikipedia.org/wiki/Chemical_bond

    A single bond between two atoms corresponds to the sharing of one pair of electrons. The Hydrogen (H) atom has one valence electron. Two Hydrogen atoms can then form a molecule, held together by the shared pair of electrons. Each H atom now has the noble gas electron configuration of helium (He).