What is the value of the Rydberg constant (Rh)?

The Rydberg constant, denoted as Rh, is a fundamental physical constant that describes the wavelengths of spectral lines of hydrogen and other hydrogen-like atoms. The value you highlighted, 2.18 x 10^-18 J, is derived from the energy level transitions of electrons in a hydrogen atom as they move between quantized energy states.

In particular, the Rydberg constant is associated with the energy levels calculated through the Rydberg formula, which provides the wavelengths of emitted or absorbed light when an electron transitions between levels. The energy of a photon emitted or absorbed during such transitions corresponds to these precise energy levels, and the Rydberg constant reflects this inherently.

The other options provided represent different physical constants: the first value corresponds to the elementary charge multiplied by voltage, the second to Planck's constant (which is involved in quantization of energy and light), and the last one is the speed of light in a vacuum. Although these constants are of great importance in various physical phenomena, they do not represent the Rydberg constant, which specifically pertains to hydrogen spectral lines and their energy transitions. Thus, the value of 2.18 x 10^-18 J accurately characterizes the energy levels in the context of this spectral