HELP
Sodium atoms emit light with a wavelength of 330 nm when an electron moves from a 4p orbital to a 3s orbital. What is the energy difference between the orbitals in kilojoules per mole?

Question

HELP 
Sodium atoms emit light with a wavelength of      330 nm when an electron moves from a 4p orbital to a 3s orbital. What is the energy difference between the orbitals in kilojoules per mole?

aaronq · Answer

use this equation to find the energy the photon has

$$E=\frac{ hc }{ \lambda }$$

h is plancks constant
c is the speed of light 
lambda is the wavelength (in meters, so you need to convert)

multiply that by avogadros number to get the value per mole.
don't forget to convert J to kJ.