The Bohr model depicts the hydrogen atom as a small, positively charged nucleus around which an electron travels in various circular orbits at specific energy levels.
The postulates of the Bohr Theory are:
a. The electron travels about the nucleus in circular orbits.
b. The only allowed orbits have specified energy levels and are at a discrete set of distances from the nucleus.
c. Electrons can gain or lose energy only by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation with a frequency f according to the equation:
d. The angular momentum L of the electron must be an integer multiple of a fixed quantity:
where n = 1, 2, 3, … is called the quantum number. It is this n that determines the size and the energy level of the various orbits.