• Electrons moves around the nucleus With fix path and fix energy. Fix path are called Orbits / stationary State / energy state / energy level.
• Energy of electron does not Change. when electron Absorbs energy It moves from Lower stationary State to higher stationary state.
When elecron moves From higher stationary state to lower stationary state It emits energy in the form of EMR
•
Energy of radiation, absorbed or emitted is equal to difference two energy state / energy of to stationary state
∆E = Ef - Ei ∆E = E2 - E1
∆E = energy of radiation Absorbs or emitted
Ef = final energy state
Ei = initial energy state
• there are stationary orbits for electron. As long as electrons revolve in these stationary orbits, they do not radiate energy. The energies of electrons remain constant in stationary orbits.
Different stationary levels or stationary orbits or shells are represented by capital letters K, L, M, N with corresponding shell number 1, 2, 3, 4, 5 etc.
• Angular momentum of electron is quanties
Angular momentum = m×v×r
M= mass of electron
V= velocity of electron
R= radius of Orbits
mvr = n(h/2π)
Angular momentum Of integral multiple of h/2π
• radius of Orbit
As the elecron of an atom revolve in one of the stationary orbital, the coulombic force of attraction of nucleus of electrons, i.e. ze2/r2 must be equal to centrifugal force of the electron mv2/r2
Hence,
Ze2/r2 = mv2/r ____(1)
R= Ze2/mv2. ______(2)
According to the Bohr's angular momentum of electron mvr is integral multiple n of h/2π
Hence, mvr = nh/2π _____(3)
V = nh/ 2πmr _____(4)
Substituting v in equation (2)
r = n2h2/4π2mZe2
Substituting values of h,m,z=1 for hydrogen and e the electronic charge r may be caculated as
r = 0.529 × n2 A°
Thus,
n = 1. r = 0.529A°
n= 2. r= 2.116A°
n= 3. r = 4.761A°
n= 4. r = 8.464A°
n= 5. r = 13.225 A°
And so on. This also suggest that electron takes up only discrete energy levels.
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