Introduction to Hydrogen Spectrum

We all know that the electrons present in either a molecule or an atom absorb the energy and get excited. They will jump from a lower energy level to a higher energy level. They also emit radiation when they return to their original states. This overall phenomenon accounts for the emission spectrum via hydrogen, too, better referred to as the hydrogen emission spectrum.

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History of Hydrogen Spectrum

In the late 1800s, it was referred to as when gas is excited with an electric discharge and the light emitted can be viewed using a diffraction grating; the observed spectrum contains not of a continuous light band, however, of individual lines with the wavelengths, that are well-defined. Several experiments have proved that the wavelengths of the lines were given as the characteristic of the chemical element that emits the light. They were an atomic fingerprint that resulted from the atom’s internal structure.

Line Spectrum of Hydrogen

The atomic hydrogen’s emission spectrum can be divided into several spectral sequences, with the wavelengths supplied using the formula of Rydberg. These noticed spectral lines are because of the electron making transitions between the two energy levels in an atom.

What is the Hydrogen Spectrum?

The hydrogen spectrum is described as an important piece of evidence to represent the quantized electronic structure of an atom. The molecule’s hydrogen atoms dissociate as soon as an electric discharge is passed via the molecule of gaseous hydrogen. It further results in the electromagnetic radiation emission initiated by the hydrogen atoms, which are energetically excited. The hydrogen emission spectrum is composed of the radiation of discrete frequencies. These radiation series are named after the scientists who have discovered them.

Hydrogen Spectrum Wavelength

When the hydrogen atom absorbs a photon, it results in causing the electron to experience a transition to the higher energy level, where n = 1,  n = 2 as an example. When a photon is emitted via a hydrogen atom, the electron undergoes a transition starting from a higher energy level to a lower, n = 3, n = 2, as an example. During this transition state from a higher level to a lower level, there occurs a transmission of light. The atom’s quantized energy levels cause the spectrum to comprise the wavelengths that reflect the differences in these energy levels. For suppose, the line at 656 nm corresponds to the transition n = 3 and n = 2.

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Hydrogen Emission Spectrum

In 1885, based on the experimental observations, Balmer proposed the formula to correlate the wavenumber of the spectral lines that are emitted and the energy shells involved. This formula can be given as follows:

\[\bar{\nu}\] = 109677 \[\left ( \frac{1}{2^{2}}-\frac{1}{n^{2}} \right )\]

This hydrogen emission spectrum series is referred to as the Balmer series. Also, this is the one and only series of lines present in the electromagnetic spectrum that exist in the visible region. The value, 109,677 cm-1, is known as the Rydberg constant for hydrogen. In general, the Balmer series is described as the part of the hydrogen emission spectrum which is responsible for the excitation of an electron starting from the second shell to any other shell. In the same way, other transitions also contain their own series names. A few of them are listed as follows:

  • Transition starting from first-shell to any other shell is called Lyman series

  • Transition starting from second-shell to any other shell is called Balmer series

  • Transition starting from third-shell to any other shell is called Paschen series

  • Transition starting from fourth-shell to any other shell is called Bracket series

  • Transition starting from fifth-shell to any other shell is called Pfund series

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The Swedish spectroscopist, Johannes Rydberg, derived a general method for measuring the hydrogen spectral line emission wavenumber due to an electron transfer from one orbit to another. The general formula for the hydrogen emission spectrum can be given as follows:

\[\bar{\nu}\] = 109677 \[\left ( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right )\]


n1 is 1, 2, 3, 4, …,

n2 is n1 +1,

𝜈 is the wavenumber of the electromagnetic radiation. The value, which is 109,677 cm-1 is referred to as the Rydberg constant for hydrogen.

Extension to the Other Systems

The Rydberg formula concepts can also be applied to any system with a single particle orbiting a nucleus. For example, a muonium exotic atom or a He+ ion. The equation must be changed according to the system's Bohr radius; emissions will be of the same character but at various energy ranges. The series of Pickering Fowler was originally attributed to an unknown hydrogen form with the half-integer transition levels by both Fowler and Pickering, whereas Bohr correctly recognized them as the spectral lines arising from the He+ nucleus.

All the other atoms possess two electrons in their neutral form at least, and the interactions between these electrons make the spectrum analysis by such simple methods, which is described as impractical. The Rydberg formula deduction was a primary step in physics, but it was much longer prior to the extension to the spectra of the other elements that could be accomplished.

FAQs (Frequently Asked Questions)

1. What is the hydrogen spectral series?

The wavelengths, which are divided into the number of spectral series by the emission spectrum were given using Rydberg formula and these wavelengths were noticed spectral lines are because of the electron making transitions between the two energy levels in an atom. The series classification using the formula of Rydberg, which was much important in the quantum mechanics development. The spectral series is also essential in astronomical spectroscopy in detecting the presence of hydrogen and calculating the redshifts.

2. Explain spectral lines in the hydrogen atom?

The atomic hydrogen’s emission spectrum can be divided into several spectral sequences, with the wavelengths supplied using the formula of Rydberg. These noticed spectral lines are because of electron-making transitions between two energy levels present in an atom.

3. Why does the hydrogen spectrum give several lines?

Whilst hydrogen holds only one electron; there are several energy levels or shells which that electron can transition between. The gaps between such levels are all different; hence each holds its own frequency resulting in various lines in the spectra.

4. What does a full spectrum mean?

Full-spectrum light is described as the light that covers the electromagnetic spectrum either from the infrared to near-ultraviolet, or all the wavelengths that are useful to animal or plant life. In specific, sunlight is considered as a full spectrum, even though the distribution of the solar spectral reaching on the Earth changes with the time of day, atmospheric conditions, and latitude.

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