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In inorganic chemistry, Fajans' rules, formulated by Kazimierz Fajans in 1923, [1] [2] [3] are used to predict whether a chemical bond will be covalent or ionic, and depend on the charge on the cation and the relative sizes of the cation and anion. They can be summarized in the following table:
For example, using 18-crown-6, potassium acetate is a more powerful nucleophile in organic solvents: [1] [K·(18-crown-6)] + AcO − + C 6 H 5 CH 2 Cl → C 6 H 5 CH 2 OAc + [K·(18-crown-6)] + Cl −. The first electride salt to be examined with X-ray crystallography, [Cs(18-crown-6) 2] + ·e −, was synthesized in 1983. This highly air- and ...
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.
In chemical graph theory and in mathematical chemistry, a molecular graph or chemical graph is a representation of the structural formula of a chemical compound in terms of graph theory. A chemical graph is a labeled graph whose vertices correspond to the atoms of the compound and edges correspond to chemical bonds.
In chemistry, a mole map is a graphical representation of an algorithm that compares molar mass, number of particles per mole, and factors from balanced equations or other formulae. [1] They are often used in undergraduate-level chemistry courses as a tool to teach the basics of stoichiometry and unit conversion. [2] [3] [4]
In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon–carbon bonds in the precursors.
A Stiff diagram, or Stiff pattern, is a graphical representation of chemical analyses, first developed by H.A. Stiff in 1951.It is widely used by hydrogeologists and geochemists to display the major ion composition of a water sample.
An electron-withdrawing group (EWG) is a group or atom that has the ability to draw electron density toward itself and away from other adjacent atoms. [1] This electron density transfer is often achieved by resonance or inductive effects.