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 = hv
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 a0 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 (z2/n2)
where: Z – atomic number
n – integer