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
NASA Star and Exoplanet Database direct access to frequently accessed tables: NStED also serves photometric time-series data from surveys that aim to discover transiting exoplanets such as "Kepler" and the CoRoT. NStED provides access to over 500,000 light curves from space and ground-based exoplanet transit survey programs, including: The transit survey data are linked to an online periodogram service that can be used to search for periods in the transit survey data sets. A user can also upload their own time series data to search for periods in their own data. The planetary orbital parameters are linked to an online transit ephemeris prediction tool which