Avy

0.3975 g of an oxide of divalent metal on reduction with hydrogen gives 0.090 g of water. The atomic weight of metal is: a) 63.5 b) 24 c) 55.5 d) 40

The longer the wavelength the less energy it has. To go from a 4p to 2s it requires a lot more energy than going from 3p to 2s. The longer wavelength will be created by the electron transition from 3p to 2s.

The principal quantum number, n , describes the energy of an electron and the most probable distance of the electron from the nucleus.

It has 1 Calcium atom (Ca), 2 Hydrogen atoms (H), 2 carbon atoms (C) and 6 Oxygen atoms (O). Adding all you get 11.