Our concepts of acids and bases have grown from the fundamental ideas of Arrhenius to Brønsted-Lowry to Lewis. The official definition is that a Lewis Acid accepts an electron pair, and a Lewis Base donates an electron pair. As a result of this, the acid is able to form a covalent bond with whatever supplies the electrons. There are two complementary definitions of acids and bases that are important: the Bronsted (or Bronsted-Lowry) definition: an acid is a proton (H+ ion) donor, and a base is a proton acceptor; the Lewis definition: an acid is an electron acceptor, and a base is an electron donor. The simplest Lewis acid is the hydrogen proton. Lewis Acid/Base Mnemonic. Lewis acid is classically restricted to species which have empty p orbital and are called trigonal planar species, for example BR3. The general form of a Lewis acid-base reaction is: Lewis base can be defined as a species or as a  basic substance that donates a lone pair of electrons to Lewis acids, in order to form a Lewis adduct. In the presence of water, the sum of acid–base interactions describes the wettability of a surface. In terms of organic chemistry, it is crucial to determine that Lewis bases are actually nucleophiles and Lewis acids are electrophiles. Figure 1. They are both Lewis bases because they can donate a pair of electron to Lewis acids. NH3 gives a lone electron pair to Me3B in a chemical reaction and forms Me3BNH3 which is a Lewis adduct. And so, one way to remember that this Lewis Base is an electron pair donor is to, if you think about this b being lowercase. Acids and Bases: Lewis vs. Bronsted. The Lewis acid–base force between a hydroxyl group and another polar molecule is also known as hydrogen bonding, one of the most important bond types found in nature, contributing to 90% of noncovalent bonding. • Bronsted defines an acid as a proton donor whereas Lewis defines an acid as an electron pair acceptor. A Lewis acid is an electron pair acceptor. These species have the ability to either accept an electron–pair or donate an electron pair. Lewis Acids and Bases Gilbert Lewis (1875–1946) proposed a third theory of acids and bases that is even more general than either the Arrhenius or Brønsted-Lowry theories. Do the practice problems associated with Section 3 Lewis Theory at the link below: http://staarhelper.com/Mr_B_Science/daily_lessons/cacid.htm, http://www.ck12.org/book/CK-12-Chemistry-Concepts-Intermediate/. May 15, 2012 < http://www.differencebetween.net/science/chemistry-science/difference-between-lewis-acid-and-base/ >. The product of a Lewis acid-base reaction is known formally as an "adduct" or "complex", although we do not ordinarily use these terms for simple proton-transfer reactions such as the one in the above example. H + has no electrons by itself. Lewis acid is classically restricted to any species which have an empty p orbital and are called trigonal planar species. For example, look at the reaction NH3 + H2O —> NH4+ + OH-. And so, an easy way to remember this is, acid acceptor. A Lewis base which holds its electrons strongly is called hard base, e.g., , etc. • Therefore, some molecules, which don’t possess protons, can be acids according to the Lewis theory. In other words, a Lewis acid is an electron-pair acceptor. In the Brnsted model, the OH-ion is the active species in this reaction it accepts an H + ion to form a covalent bond. Gilbert Newton Lewis (same Lewis who is behind the electron-dot formulas) suggested even a more general way of classifying acids and bases. Other molecules can also act as either an acid or a base. A Lewis acid is a chemical species being able to accept an electron-pair, reacting thereby with a Lewis base to form a Lewis bond, ie. Lewis base can be defined as a species or basic substance which donates a lone pair of electrons to Lewis acids in order to form a Lewis adduct. For example, OH− and NH3 are Lewis bases, because they can donate a lone pair of electrons. Gilbert Lewis (1875–1946) proposed a third theory of acids and bases that is even more general than either the Arrhenius or Brønsted-Lowry theories. The reaction between ammonia and the hydrogen ion can be depicted as shown in the Figure 1. As there is no hydrogen ion involved in this reaction, it qualifies as an acid-base reaction only under the Lewis definition. What is the definition of an Arrhenius acid or a Lewis base or even a Bronsted-Lowry acid or base? 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