Niels Bohr AtomicTheory
Modern atomic structure isa result of work of lot many generations of scientists. Many theorieswere put forward, and some concepts accepted, while some rejected,before a complex, modern atomic structure was arrived at.
Avery important milestonein the discovery of atom was the Bohr’s theory, put forward byNiels Bohr.
Rutherford’s atomicmodel could not explain the emission of electromagnetic radiation andso, it could not explain the existence of spectral lines even for thesimplest atom, hydrogen.
In order to overcome thedifficulties encountered in Rutherford’s model, Niels Bohr, putforward a theory in 1913.
The postulates of NielsBohr atomic theory are:
The electrons in anatom revolve around the nucleus only certain selected circularorbits. The orbits are related with definite energies and aretherefore called energy shells or energy levels. These are numberedas 1, 2, 3, 4, etc., or designated as K, L, M, N...etc. shells.
The orbits which arepermitted are having the angular momentum of the electron as a wholenumber multiple of h/2π, where h is Plank’s constant. Angularmomentum of the electron, mvr = nh/2π, where n="1," 2, 3, …n.
Where,m is the mass of the electron, v is the velocity of the electron andr is the radius of the orbit.
n =number of the orbit in which the electron is present.
The orbits occupiedby electrons, are said to be stationary orbits. The energy of anelectron, if it remains in that particular orbit, remains constant.This state, where an electron keeps revolving, without losing energyis said to be the ground state.
When an electronjumps from one orbit to another, energy of the electron is absorbedor emitted. Energy is absorbed, when an electron jumps from lowerenergy level to higher energy level, while energy is emitted, whenthe electron jump from a higher energy level to a lower energylevel.
∆E =E2 – E3= hv = hc/λ
Whereh = Plank’s constant, v = frequency of radiation absorbed oremitted, c = velocity of light, ∆E indicates the difference inenergy.
Forthcoming post is on the topic periodic table families and groups keep reading my blogs.
According to Niels Bohratomic model, when the electron moves from inner to outer orbit byabsorbing a definite amount of energy, the new state of electron issaid to be the excited state.
One of the demerits ofBohr’s theory of hydrogen is that though it successfully explainshydrogen emission spectrum, it does not explain the spectra ofmulti-electron atoms.
Learn Representative Elements Periodic Table online keep checking blogs for more help.
Niels Bohr model suggeststhat electrons keep revolving around the nucleus in the stationarystates so that the electrostatic attractions between the nucleus andthe electrons are balanced by the centrifugal forces of the orbitingelectrons.