Bohr atomic model & spectral lines (3D)
About this app
The electron jumps between quantized orbits (Eₙ = −13,6 eV·Z²/n²); on a downward jump a photon is emitted and the corresponding spectral line lights up in the emission spectrum (Lyman/Balmer/Paschen). Hydrogen or He⁺.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
Quantised orbits and light quanta
In 1913 Niels Bohr proposed that the electron in a hydrogen atom circles only on certain orbits with fixed energies: Eₙ = −13.6 eV · Z²/n². When it jumps from a higher to a lower orbit it emits the energy difference ΔE as a photon; to jump up it must absorb a photon of that energy. The wavelength follows from λ = h·c/ΔE, roughly 1240 nm divided by ΔE in eV. Each transition thus produces a sharp spectral line, and together they form the element’s line spectrum.
What the app shows
Six labelled orbits surround a glowing nucleus, and the electron circles on one of them. On a downward jump a photon in the colour of its wavelength flies off, and the line lights up in an emission spectrum below the atom, where it collects with earlier lines. On an upward jump a photon flies in. The readout gives energy ΔE, wavelength λ, the series and the range: Lyman in the ultraviolet, Balmer in the visible, Paschen in the infrared.
What you can try
Choose a target level between n = 1 and n = 6 and make the electron jump. Collect the Balmer lines one by one, such as Hα at 656 nm in red and Hβ at 486 nm in blue-green. Switch to the helium ion He⁺ with Z = 2: all energies are multiplied by four and the lines move far into the ultraviolet. “Clear spectrum” starts the collection over.
Frequently asked questions
- What does the Bohr model of the atom say?
- In Bohr’s 1913 model electrons circle only on allowed orbits with fixed energies and do not radiate there. Light is emitted or absorbed only when the electron switches between two orbits, as a photon carrying exactly the energy difference. The model explains hydrogen’s spectral lines exactly but fails for atoms with several electrons and was superseded by quantum mechanics.
- What is the Balmer series?
- The Balmer series contains all hydrogen transitions that end on level n = 2. Its first lines are visible: Hα at 656 nm (red, from n = 3), Hβ at 486 nm (from n = 4), Hγ at 434 nm and Hδ at 410 nm. Transitions to n = 1 form the Lyman series in the ultraviolet, transitions to n = 3 the Paschen series in the infrared.
- How do you calculate the wavelength of a hydrogen spectral line?
- Take the energy difference between the two levels using Eₙ = −13.6 eV/n² and insert it into λ = h·c/ΔE. For the transition from n = 3 to n = 2, ΔE = 13.6 eV · (1/4 − 1/9) ≈ 1.89 eV, so λ ≈ 1240 nm/1.89 ≈ 656 nm, the red Hα line.
- What can I try out in this app?
- You choose a target level, make the electron jump and see the emitted or absorbed photon. Energy, wavelength, series and spectral range are shown, and the lines collect in the spectrum. You can switch between hydrogen and He⁺.
Subject: Physics experiments (Deutsches Museum)
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