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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Photon

A particle (quantum) of light. Each photon carries energy E=hν=hc/λE = h\nu = hc/\lambda, and atoms and molecules absorb or emit light one photon at a time.

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 = 3 to n = 2 (emission).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 Jemission

An H atom dropping from n=3n = 3 to n=2n = 2 emits one 656 nm photon.

Example

A 656 nm photon from hydrogen carries E=(6.626×10−34)(2.998×108)656×10−9=3.03×10−19E = \dfrac{(6.626\times10^{-34})(2.998\times10^{8})}{656\times10^{-9}} = 3.03\times10^{-19} J.

See alsoPlanck's constantFrequencyWave–particle dualityPhotoelectric effect