Which Bohr diagram shown above represents the purple band seen in the hydrogen emission spectra (below)? The red band? The blue band? The blue-green band? Explain how you know.

Question

Answer 1

Each of these bands falls to the same energy level, n = 2, so we know that each falls within the Balmer series, which ejects photons with wavelengths in the visible spectrum.

To evaluate which photon will relate to each color:

1. First, we know that Energy & Wavelength are inversely related: E = hf / λ
2. Second, given that all electrons in Fig. A–D are falling to the same energy level (n = 2), falling from higher energy levels (ex. n= 6 ––> n = 2) relates to releasing greater energy.
3. Third, each diagram describes the energy levels fallen and the frequency of each ejected photon:
4. Fig. A – n = 6 ––> n = 2, highest Energy, shortest λ (PURPLE)
5. Fig. B – n = 5 ––> n = 2, 2nd highest Energy, 2nd shortest λ (BLUE)
6. Fig. C – n = 4 ––> n = 2, 2nd lowest Energy, 2nd longest λ (GREEN)
7. Fig. D – n = 3 ––> n = 2, lowest Energy, longest λ (RED)

Hope this provides some clarity of the relationship between the Bohr model, photon energy, and wavelength!