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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Paschen series

The hydrogen lines that end on (emission) or start from (absorption) n=3n = 3. The gaps are small, so all Paschen lines are infrared, from 1875 nm (4→34 \to 3) down to the 820 nm series limit.

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; n = 5: −8.72 × 10⁻²⁰ J. Arrow from n = 4 to n = 3 (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 Jn = 5−8.72 × 10⁻²⁰ Jemission

4→34 \to 3, the first Paschen line (1875 nm).

Example

5→35 \to 3: 1/λ=(1.097×107)(19−125)=7.80×105 m−11/\lambda = (1.097\times10^{7})(\tfrac19 - \tfrac{1}{25}) = 7.80\times10^{5}\ \mathrm{m^{-1}}, so λ=1282\lambda = 1282 nm (IR).

See alsoBalmer seriesInfrared (IR)Series limit