An emission line of sodium has a wavelength of 330 nm. Calculate the energy of a photon of light emitted in J/atom, and the energy emitted per mole of Na atoms in kJ/mol at this wavelength.

Energy = 6.0236 X 10 ^-19J per atom and  362.80KJ/mol

Explanation:

The energy of a photon is given by:

E = hf

but f =c/ λ

therefore E= = hc/ λ

Where h is the Planck constant, 6.626x10^-34 J*s

c = speed of light =  3.0 x 10 ^ 8 m/s

λ n= wavelength = 330nm

but  10^9 nm = 1m

330nm= 3.30 x 10^-7m

E= 6.626 X 10 ^-34Js  X3.0 x 10 ^ 8 m/s / 3.30 x 10^-7m

= 6.0236 X 10 ^-19J per atom ---Which is  energy of a single photon,

Now 1 mole =  6.022x10^23 units, (Avogadro number)

therefore , the  energy per  1 mole of photons is

6.0236 x 10^-19 J/atm X 6.023 X 10 ^23 atm/ 1 mol = 362,803.618J/mol

changing to KJ/mol becomes    362,803.618/ 1000= 362.80KJ/mol

neutrons are in the middle of the atom and the electrons, which are much smaller.