Calculate the wavelength (in nanometers) of a photon emitted by a hydrogen atom when its electron drops from the n = 5 to n = 3 state

Need what is special about water as a compound? how does water regulate climate? what drives water evaporation?   why is the water vapor fresh water when it rises from the ocean? why might freshwater in the form of snow take longer to enter the water cycle again than liquid precipitation?   what is an aquifer? what role do people play in the water cycle? plz just answer as many as you can ! thx if you !

When a beta particle is emitted, the mass number of the nucleus a. decreases by one b. increases by one c. remains the same d. decreases by two

Volume is a measurement of how fast particles of a substance are moving