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Chemistry · Glossary

What is Energy level, ground state, excited state?

Also known as: energy level · ground state · excited state

Definition 1.1 University Chemistry — Year 1 · Chapter 1 — Quantum Numbers and Electron Configurations

The energy of an electron bound in an atom can take only certain values, the energy levels of the atom. The zero of energy is taken when the electron is at rest infinitely far from the nucleus (the atom is ionised), so every level of a bound electron is negative. The lowest level is the ground state; every other level is an excited state.

The energy levels of hydrogen, E_n = -13.6\, eV/n2, drawn to scale (computed from the Rydberg constant); the levels n = 4, 5, … crowd below zero. Each arrow is one emitted photon; arrows ending on the same level form a series.
The energy levels of hydrogen, En=−13.6 eV/n2E_n = -13.6\,\mathrm{eV}/n^2, drawn to scale (computed from the Rydberg constant); the levels n=4,5,…n = 4, 5, \dots crowd below zero. Each arrow is one emitted photon; arrows ending on the same level form a series.
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