The Chemistry of Art > 2. The Structure of the Atom and Colours > The Development of The Bohr Model >

**The development of the Bohr model of the atom from the hydrogen spectra and relate energy levels to electron shells**

- Atomic spectrum of Hydrogen
- Produced via excitation of atoms and release of excess energy through emission of light of various wavelengths
- Described as discrete line spectrum, indicating that only certain energies are possible which means that energy levels are quantized.
- Max Planck formulated the relationship between frequency and energy in Quantum theory
- Electromagnetic (EM) radiation is transmitted or absorbed in discreet units (quanta) often referred to as “photons”
- The energy of photon (E) is directly proportional to its frequency (v)

E = h*v*

where h – Planck’s constant (6.626 x 10^{-34} J-s)

v – frequency (in Hertz or s^{-1})

- Neils Bohr applied Planck’s concept to explain the hydrogen spectrum by proposing a quantum model.

**Quantum model of hydrogen atom**

- In a hydrogen atom, the electron moves around the nucleus only in certain allowed circular orbits
- Using classical physics, Bohr was able to calculate the radii of such allowed orbits – later called as “Bohr orbit”
- Bohr orbit – has symbol of a
_{0 }with corresponding value of 5.29 x 10^{-11}m

- – radius of the orbit of H atom closest to the nucleus

- The energy levels (in Joules) available to the electron in H atom can be calculated using the equation derived by Bohr.

E = -2.178 x 10^{-18 }J (z^{2}/n^{2})

where: Z – atomic number

n – integer