Sodium atoms emit a spectral line with a wavelength in the yellow, 589.6 nm. What is the approximate — Atomic Structure Chemistry Question

💡 Solution & Explanation

Energy difference $\Delta E = \frac{hc}{\lambda} = \frac{1240 \text{ eV}\cdot\text{nm}}{589.6 \text{ nm}} \approx 2.1$ eV. In Joules, this is $2.1 \times 1.6 \times 10^{-19} \approx 3.36 \times 10^{-19}$ J. In kcal/mol, it's $2.1 \text{ eV} \times 23.06 \text{ kcal/mol/eV} \approx 48.4$ kcal/mol. Thus, all options are approximately correct. Therefore, correct answer is D.