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How does spectroscopy reveal information about atomic structure?

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A diagram of a cylindrical vessel containing gas, with a movable piston held down by a weight. Countless small dots beneath the piston represent gas particles in rapid, random motion, illustrating Bernoulli's model of gas pressure. — physics As conceived by Daniel Bernoulli in *Hydrodynamica* (1738), gases consist of numerous particles in rapid random motion. He assumed that the pressure of a gas is produced by the direct impact of the particles on the walls of the container.

Spectroscopy reveals information about atomic structure by analyzing the discrete energy levels of atoms, which are determined by the arrangement of their electrons. Because atoms exist in specific quantum states, they can only absorb or emit electromagnetic radiation at frequencies corresponding to the energy difference between these states.123

This process occurs in two primary ways:
* Emission: When an atom is excited to a higher energy state, it spontaneously releases that energy as a photon while returning to a lower state. The frequency ( $ν$ ) of this light is defined by the relationship $E = h ν$ , where $h$ is Planck’s constant.14
* Absorption: An atom absorbs a photon of a specific energy to transition from a lower state to a higher one, creating dark lines in a spectrum.45

By measuring these spectral lines, scientists can determine the energy states of an atom. Comparing these measurements to quantum mechanical calculations allows researchers to map the electronic structure of matter, providing deep insights into the physical and chemical properties of elements.1426