Download Model of the Atom: Bohr`s Theory

Model of the Atom: Bohr's Theory
written by: Ricky • edited by: Lamar Stonecypher • updated: 7/5/2009
Have you ever wondered how the invisible atoms and their components are relevant to important phenomenon such
as electricity? You need to know the basics before you even start on this journey and this article helps you in that.
Introduction
Electricity is all about the flow of electrons so basically the subatomic level of matter plays an important part in all
electrical phenomenons in a subtle manner. Hence it is very important to properly understand the structure of the
atom in order to understand electricity. Various models of the atom have been put forward by various scientists and
researchers over a period of time. Some of these models were discarded due to anomalies in theory and observation
while others have been modified in light of new experiments. We will study one such model which is important
from the electrical engineering point of view, and that is that Neil Bohr's atomic model which we will study in this
article.
Neils Bohr’s Atomic Model
As the name itself suggests, this model of atomic structure was proposed by a scientist named Neils Bohr nearly a
century ago, in the year 1913. The main reason for Bohr to put forward this theory just two years after Rutherford
has proposed his theory was to explain some serious flaws in the latter. The Bohr’s model was based on the
Quantum Theory and the main points of the model are as follows.

Bohr suggested that the major part of the atomic mass was concentrated at the center of the atom which is
known as the nucleus and is positively charged. Of course this was same as Rutherford’s theory. Bohr’s theory
also confirmed regarding orbital motion of the electrons around this nucleus.

Since a rotating body experiences centrifugal force which tries to throw the body outwards, it has to be
balanced by some inward force. This is provided by the electrostatic force of attraction between the positively
charged nucleus and the negatively charged electrons.

The main difference between the Bohr’s model vis-à-vis Rutherford’s model is that the former does not allow
electrons to revolve in any arbitrary model around the nucleus but only in discrete orbits. The angular
momentum of the electrons in these orbits is equal to the integral multiple of a certain constant number. The
constant is experimentally calculated as h/2Π where h is known as Planck’s constant.

Because of the fact that the orbits are not arbitrary but discrete, they are known as stationery orbits. They are
also known as non-radiating orbits since the theory also states that an electron cannot radiate any energy while
being in the same orbit. The adjacent diagram clearly shows the model of the atom in a colourful manner and
the various components of the atom are clearly labeled.

An electron can only emit (or absorb) energy if it jumps from an orbit with higher energy to lower energy (or
vice versa). The equation which gives the amount of energy emitted in such a transition is given by the
formula dE = h * f where dE is energy change, h is Planck’s constant and f is frequency of emitted radiation.
Of course the above discussion is limited to Bohr’s model which is sufficient for the purposes of basic electricity
explanation; yet this theory has several flaws and they have been addressed by other proposals such as the cloud
theory. There were models in the past even before Rutherford’s model such as those proposed by Dalton, Thompson
etc and there will be models in future also till the mystery of the atom gets resolved completely.
Source:
http://www.brighthubengineering.com/diy-electronics-devices/41407-model-of-the-atom-bohrstheory/