Chemistry: The Central Science (13th Edition)

$\Delta E$ would be positive in this electronic transition.
The change of energy $(\Delta E)$ is: - positive when the electron moves from a lower state (lower energy) to a higher state (higher energy). - negative when the electron moves from a higher state (higher energy) to a lower state (lower energy). The electron here moves from n = 4 to n = 9, meaning that it moves from a lower state to a higher state. Therefore, $\Delta E$ would be positive.