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
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