Lewis acids and bases studied chemical bonding. In 1923, Lewis wrote "An acid substance is one which can employ an electron lone pair from another molecule in completing the stable group of one of its own atoms." The Brønsted–Lowry acid–base theory was published in the same year. The two theories are distinct but complementary. A Lewis base is also a Brønsted–Lowry base, but a Lewis acid doesn't need to be a Brønsted–Lowry acid. The classification into hard and soft acids and bases (HSAB theory) followed in 1963. The strength of Lewis acid-base interactions, as measured by the standard enthalpy of formation of an adduct
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