BOHR'S MODEL OF THE ATOM...
In
order to explain stability of atom and to overcome the objection of Rutherford's model
of atom , Neils
Bohr put forward his atomic model in
1913. Bohr's atomic model can be explained as follows:
1) An atom is made up of three(03) parts protons(having
positive charge) , neutrons(having no charge) and electrons(having negative charge).
Due the presence of equal numbers of protons and electrons , the atom is electrically
neutral.
2) The
protons and neutrons are present at the center in the nucleus of the atom which
results in positive charge on nucleus of atom due to the presence of protons in
it.
3) The
electrons revolve continuously around the nucleus in fixed paths called as energy
levels or shells. These shells are represented in two ways either by numbers i.e1,2,3,4,5,6
or by letters i.e k,l,m,n,o,p. The energy levels are counted from centre outwards.
4) There
is a limit for each energy level to hold a particular number of electrons.
5) Each
energy level is associated with a fixed, energy the inner shell consists minimum
energy while the outer most shell contains a maximum energy in it.
6) There
is no change in energy of electron until continues in rotating in the same energy
level and the atom remains stable. the change in the energy level of electrons increases or decreases only when they lose or gain
energy by changing their shells.
Pastulates_Of_Rutherfords_Model_Of_ Atom...
1) Atom consists of a positively charged center, the nucleus.
2) At a considerable distance from the nucleus, the electrons were orbiting in a manner much like the way the planets orbit the sun. Hence this model is also called as planetary model of atom.
3) The no. of electrons in the orbit is equal to the no. of protons in the nucleus. Hence the atom is electrically neutral.
4) The volume of nucleus is negligible small as compared to the volume of atom.
5) Hence, most of the space in the atom is empty.
DRAWBACK OF RUTHERFORD'S MODEL OF ATOM...
There are
some drawbacks (defects) in the Rutherford's model but the main drawback in his theory
is that he don't have explained anything about the stability of atom. This will
become more clear from the discussion below.
Ruherford in his model has proposed that
negatively charged particles known as electrons revolve around the nucleus of atom
which has positive charge in cicular paths. But we know that when an object rotates
in circular path it starts accelerating.
According
to the electromagnetic theory of physics if a charged particle undergoes accelerated
motion in circular path then it must lose energy in form of radiations now if we
apply this electromagnetic theory to rutherford's model then it implies that while
these electrons revolve they continously loose their energy and gradually their
speed decreases and they gets attracted by the nucleus of atom and finally they
will fall in the nucleus hence which will result in making atom very unstable and
will collapse.
But
this doesnt' happen at all and electrons did not fall in the nucleus of atom. And did
not collapse on its own and this is the main problem with rutherford's model of
atom.
Also read:
Also read:
No comments:
Post a Comment
Tell Us What You've Got...