Question: What type of acid was named for the discoverer of the covalent bond?

<P0-S0> A symmetric hydrogen bond is a special type of hydrogen bond in which the proton is spaced exactly halfway between two identical atoms. <P0-S1>  The strength of the bond to each of those atoms is equal. <P0-S2>  It is an example of a 3-center 4-electron bond. <P0-S3>  This type of bond is much stronger than "normal" hydrogen bonds, in fact, its strength is comparable to a covalent bond. <P0-S4>  It is seen in ice at high pressure (Ice X), and also in the solid phase of many anhydrous acids such as hydrofluoric acid and formic acid at high pressure. <P0-S5>  It is also seen in the bifluoride ion [F−H−F]. <P0-S6>  Much has been done to explain the symmetric hydrogen bond quantum-mechanically, as it seems to violate the duet rule for the first shell: The proton is effectively surrounded by four electrons. Because of this problem, some consider it to be an ionic bond. <SEP> <P1-S0> The covalent bond classification (CBC) method is also referred to as the LXZ notation. <P1-S1>  It was published by M. L. H. Green in the mid-1990s as a solution for the need to describe covalent compounds such as organometallic complexes in a way that is not prone to limitations resulting from the definition of oxidation state. <P1-S2>  Instead of simply assigning a charge to an atom in the molecule (i.e. the oxidation state), the covalent bond classification method analyzes the nature of the ligands surrounding the atom of interest, which is often a transition metal. <P1-S3>  According to this method, there are three basic types of interactions that allow for coordination of the ligand. <P1-S4>  The three types of interaction are classified according to whether the ligating group donates two, one, or zero electrons. <P1-S5>  These three classes of ligands are respectively given the symbols L, X and Z. <SEP> <P2-S0> A Lewis acid is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. <P2-S1>  A Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. <P2-S2>  For example, NH is a Lewis base, because it can donate its lone pair of electrons. <P2-S3>  MeB is a Lewis acid as it is capable of accepting a lone pair. <P2-S4>  In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. <P2-S5>  In the context of a specific chemical reaction between NH and MeB, the lone pair from NH will form a dative bond with the empty orbital of MeB to form an adduct NH•BMe. <P2-S6>  The terminology refers to the contributions of Gilbert N. Lewis. <SEP> <P3-S0> Gilbert Newton Lewis {'1': ", '2': ", '3': 'ForMemRS', '4': "} (October 25 (or 23), 1875 – March 23, 1946) was an American physical chemist known for the discovery of the covalent bond and his concept of electron pairs; his Lewis dot structures and other contributions to valence bond theory have shaped modern theories of chemical bonding. <P3-S1>  Lewis successfully contributed to thermodynamics, photochemistry, and isotope separation, and is also known for his concept of acids and bases.