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HSAB is an acronym for "hard and soft (Lewis) acids and bases".HSAB is widely used in chemistry for explaining the stability of compounds, reaction mechanisms and pathways. It assigns the terms 'hard' or 'soft', and 'acid' or 'base' to chemical species.
The following is its formal definition: If X is a formula with a classical bivalent truth value (which must be either true or false), then X can be read as "X is possibly true". [14] Lewis then defined "A strictly implies B" as " (A B)". [15]
The most common Lewis bases are anions. The strength of Lewis basicity correlates with the pK a of the parent acid: acids with high pK a 's give good Lewis bases. As usual, a weaker acid has a stronger conjugate base. Examples of Lewis bases based on the general definition of electron pair donor include: simple anions, such as H − and F −
In stereochemistry, enantiomeric excess (ee) is a measurement of purity used for chiral substances. It reflects the degree to which a sample contains one enantiomer in greater amounts than the other. A racemic mixture has an ee of 0%, while a single completely pure enantiomer has an ee of 100%. A sample with 70% of one enantiomer and 30% of the ...
(Lewis acid) Any chemical species or molecular entity that acts as an electron pair acceptor when reacting with another species, forming a covalent bond by accepting a lone pair of electrons donated by the other species, which is known as a Lewis base. This definition was intended as a generalization of the Brønsted–Lowry definition by ...
However when counting electrons, negative ions should have extra electrons placed in their Lewis structures; positive ions should have fewer electrons than an uncharged molecule. When the Lewis structure of an ion is written, the entire structure is placed in brackets, and the charge is written as a superscript on the upper right, outside the ...
Lewis lived with and cared for Moore until she was hospitalized in the late 1940s. He routinely introduced her as his mother, referred to her as such in letters, and developed a deeply affectionate friendship with her. Lewis's own mother had died when he was a child, while his father was distant, demanding, and eccentric.
Hard science and soft science are colloquial terms used to compare scientific fields on the basis of perceived methodological rigor, exactitude, and objectivity. [ 1 ] [ 2 ] [ 3 ] In general, the formal sciences and natural sciences are considered hard science , whereas the social sciences and other sciences are described as soft science .