Lewis acids and bases Lewis acids and bases 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. 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. For example, NH is a Lewis base, because it can donate its lone pair of electrons. Trimethylborane (MeB) is a Lewis acid as it is capable of accepting a lone
Magic cube classes MAY be pandiagonal magic. Gardner also called this (Langman’s pandiagonal) a ‘perfect’ cube, presumably not realizing it was a higher class then Myer’s cube. See previous note re Boyer and Trump. <br>The smallest normal pandiagonal magic cube is order 7. See Pandiagonal magic cube.<br>Minimum correct summations required = 9"m" + 4. All pan-"r"-agonals sum correctly for "r" = 1 and 2. ALL 3"m" planar arrays must be pandiagonal magic squares. In addition, ALL pantriagonals must sum correctly. These two conditions combine to provide a total of 9m pandiagonal magic squares. <br>The smallest normal perfect magic cube is order 8. See