Powerpoint Presentation on the Chapter "Structure Of Atom" from 9th Class Science

1. STRUCTURES
OF ATOM
B Y- A K S H U N C H A U H A N
C L A S S - 9 D
R O L L N O . - 2 8

2. Index
1. About Atom
2. JJ Thomson Model
3. Rutherford Model And Experiment
4. Neil Bohr's Model
5. Erwin Schrödinger Model
6. Question

3. Atoms and Sub-Atomic
particles.
• Atom is the fundamental unit of matter.
• All forms of matter are made up of atom. Eg-
Hydrogen(H), Oxygen(O).
Sub atomic particles-
I) Electron- Negatively charged
II) Proton- Positively charged
III) Neutron- Neural body

4. Thomson's Model Of Atom
• JJ Thomson was the first to propose model
of structure of atom.
• As per his model, atom
comprises a positively charged sphere
with electrons embedded in it, (like a
watermelon or plum pudding).
• He explained that atom is
neutrally charged as amount of positive
and negative charge is equal.

5. His Study and
Conclusion
• He is credited for
discovering the electron.
• He used his research on
cathode ray tube
technology in this
discovery.

6. Ernst Rutherford
• Ernest Rutherford was not
convinced about the model of
the atom proposed by
Thomson.
• He thus set up his now
famous Gold Foil Experiment.

7. Gold Foil α Particle
Experiment
1. He fired alpha particles
(positively charged) at a gold
foil.
2. He measured the deflection as
the particles came out the
other side.
3. Most of the particles did not
deflect at all.
4. He said that there must be a
positive centre of the foil. He
called this centre the nucleus.

8. RUTHERFORD’S ATOMIC MODEL
• The nucleus of the atom is a dense
mass of positively charged particles.
• The electrons orbit the nucleus
Drawbacks of his Model
• As per Maxwell's theory of electro
magnetics, when a charged particle is
accelerated, it must loose energy.
• In this case, if electrons loose energy, it
will slow down and fall into the
nucleus.

9. Neil Bohr
• Niels Bohr agreed with the
planetary model of the atom, but
also knew that it had a few flaws.
• Using his knowledge of energy
and quantum physics he was
able to perfect Rutherford’s
model.
• He was able to answer why the
electrons did not collapse into
the nucleus.

10. BOHR’S ATOMIC
MODEL
 1. Electrons orbit the nucleus in
orbits that have a set size and
energy.
 2. The lower the energy of the
electron, the lower the orbit.
 3. This means that as electrons
fill up the orbitals, they will fill
the lower energy level first.
 4. If that energy level is fill (or
at capacity), a new energy level
will begin.

11. Conclusion
Bohr estimated the distance of shell from the nucleus.
He gave the velocity of electrons in different shells.
He also estimated the value of enrgy in different shells.

12. Schrödinger Model (Cloud Model)
 Erwin Schrödinger was a revolutionary physicist
who used Heisenberg’s uncertainty principle to
come up with the atomic model that we still use
today.
Conlcusion-
 1. An electron does not travel in an exact orbit
 2. We can predict where it will probably be
 3. We cannot say for certain where it is, but only
where it ought to be.
 4. The type of probability orbit is dependent on
the energy level described by Bohr

13. Questions