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# Sodium atom emits light with a wavelength of 330nm when an electron moves from a 4p orbital to a 3s orbital. what is the energy difference between the orbitals in KJ/mol?

$(a)\;362KJ/mol\qquad(b)\;632.42KJ/mol\qquad(c)\;232.4KJ/mol\qquad(d)\;143.32KJ/mol$

$\lambda = 300nm=330\times10^{-9}m$
$E=N_{\large\circ}hv=\large\frac{N_{\large\circ}hc}{\lambda}$
$=\large\frac{6.02\times10^{23}\times6.626\times10^{-34}\times3\times10^8}{330\times10^{-9}}$
$=362.62\times10^3$J/mol
=362.62 KJ/mol
Hence anwer is (a)