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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Excited state

Any state of higher energy than the ground state. An atom reaches one by absorbing a photon (or through heat or an electric discharge) and returns to lower levels by emitting photons.

Energy levels of the hydrogen atomn = 1: −2.18 × 10⁻¹⁸ J; n = 2: −5.45 × 10⁻¹⁹ J; n = 3: −2.42 × 10⁻¹⁹ J; n = 4: −1.36 × 10⁻¹⁹ J. Arrow from n = 1 to n = 2 (absorption).n = ∞0 Jn = 1−2.18 × 10⁻¹⁸ Jn = 2−5.45 × 10⁻¹⁹ Jn = 3−2.42 × 10⁻¹⁹ Jn = 4−1.36 × 10⁻¹⁹ Jabsorption

Absorbing a 122 nm photon lifts hydrogen from n=1n = 1 into its first excited state, n=2n = 2.

Example

Exciting H from n=1n = 1 to n=2n = 2 takes ΔE=RH(1−14)=1.634×10−18\Delta E = R_H(1 - \tfrac{1}{4}) = 1.634\times10^{-18} J, a 122 nm ultraviolet photon.

See alsoGround stateEnergy levelPhotonEmission spectrum