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
Magic Tree House Magic Tree House Merlin Mission Books 1-27 were written for more advanced readers. They are more challenging adventures for readers ages 7–10. The Magic Tree House Merlin Missions were originally ordered sequentially, starting at Book #29 (Christmas in Camelot). With the 25th anniversary re-prints, the books have been separated into their own distinct series and re-numbered starting at Merlin Mission #1. On January 6, 2015, the first Magic Tree House Super Edition was released. It is 183 pages long. The super editions are longer than the original Magic Tree House books and the Magic Tree House Merlin Missions. The Magic