Electronic Structure and Quantum Models (4E) Practice Test

In a study of oxidative stress, a researcher compares the reactivity of elemental oxygen in two different electronic states: ground-state $\text{O}_2$ and singlet oxygen ($^1\text{O}_2$). The enhanced reactivity of $^1\text{O}_2$ is linked to a different electron arrangement in the highest occupied molecular orbitals. Which principle best explains the observed electron behavior?

In a phototherapy development study, a heme-mimetic porphyrin complex is doped with trace amounts of sodium to provide a stable internal calibration line. Emission spectroscopy shows a sharp line at $\lambda = 589\ \text{nm}$ that is unchanged by solvent polarity. The investigators attribute this line to an electronic transition in Na atoms from a $3p$ state to a $3s$ state. Use $h = 6.63\times 10^{-34}\ \text{J}\cdot\text{s}$ and $c = 3.00\times 10^8\ \text{m/s}$. Based on the quantum model, which outcome is most consistent with this assignment?