Lewis acids and bases ionic bonding. Classically, the term "Lewis acid" is restricted to trigonal planar species with an empty p orbital, such as BR where R can be an organic substituent or a halide. For the purposes of discussion, even complex compounds such as EtAlCl and AlCl are treated as trigonal planar Lewis acids. Metal ions such as Na, Mg, and Ce, which are invariably complexed with additional ligands, are often sources of coordinatively unsaturated derivatives that form Lewis adducts upon reaction with a Lewis base[citation needed]. Other reactions might simply be referred to as "acid-catalyzed" reactions. Some compounds, such as HO, are
Nasik magic hypercube original definition of nasik.<br> A "nasik" magic cube would have 13 magic lines passing through each of its "m" cells. (This cube also contains 9"m" pandiagonal magic squares of order "m".)<br> A "nasik" magic tesseract would have 40 lines passing through each of its "m" cells.<br> And so on. In 1866 and 1878, Rev. A. H. Frost coined the term "Nasik" for the type of magic square we commonly call "pandiagonal" and often call "perfect". He then demonstrated the concept with an order-7 cube we now class as "pandiagonal", and an order-8 cube we class as "pantriagonal".<br> In another 1878