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  2. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    This article needs attention from an expert in chemistry. ... "First 25 of 125 big questions that face scientific inquiry over the next quarter-century".

  3. Chemistry - Wikipedia

    en.wikipedia.org/wiki/Chemistry

    Chemistry is the scientific study of the properties and behavior of matter. [1] It is a physical science within the natural sciences that studies the chemical elements that make up matter and compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during reactions with other substances.

  4. Simmons–Smith reaction - Wikipedia

    en.wikipedia.org/wiki/Simmons–Smith_reaction

    Thus, cyclohexene, diiodomethane, and a zinc-copper couple (as iodomethylzinc iodide, ICH 2 ZnI) yield norcarane (bicyclo[4.1.0]heptane). [5] [6]The Simmons–Smith reaction is generally preferred over other methods of cyclopropanation, [7] however it can be expensive due to the high cost of diiodomethane.

  5. Conservation of mass - Wikipedia

    en.wikipedia.org/wiki/Conservation_of_mass

    The law of conservation of mass can only be formulated in classical mechanics, in which the energy scales associated with an isolated system are much smaller than , where is the mass of a typical object in the system, measured in the frame of reference where the object is at rest, and is the speed of light.

  6. Baldwin's rules - Wikipedia

    en.wikipedia.org/wiki/Baldwin's_rules

    The rules apply when the nucleophile can attack the bond in question in an ideal angle. These angles are 180° (Walden inversion) for exo-tet reactions, 109° (Bürgi–Dunitz angle) for exo-trig reaction and 120° for endo-dig reactions. Angles for nucleophilic attack on alkynes were reviewed and redefined recently. [4]

  7. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    It is an icon of chemistry and is widely used in physics and other sciences. It is a depiction of the periodic law, which states that when the elements are arranged in order of their atomic numbers an approximate recurrence of their properties is evident. The table is divided into four roughly rectangular areas called blocks. Elements in the ...

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