Rutherford conducted an experiment where he fired alpha particles at a thin gold foil. Most particles passed through without deflection, but some were deflected at small angles and a few were reflected back. This led Rutherford to propose an atomic model where the atom consists of a very small, dense, positively charged nucleus surrounded by electrons in orbits. However, his model did not explain atomic stability as it predicted electrons would radiate energy and spiral into the nucleus.

1. RUTHERFORD
ATOMIC
MODEL
NAME:
CLASS: IX
ROLL NO.:

2. CONTEXT
• Alpha Particle
• Experimental Set up
• Observation
• Rutherford Atomic Model of an Atom
• Drawback of Rutherford Atomic Model of an Atom
• Conclusion

3. ALPHA PARTICLE
Alpha particles is a positively charged
particle having 2 units of positive charge
and 4 units of mass. They are emitted
from radioactive elements like Radium
and Polonium. The fast moving alpha
particles have considerable amount of
energy. They can penetrate through the
matter.

4. EXPERIMENTAL SET UP
• He Select a thin gold foil
• The fast moving alpha particles are allowed to strike a very thin gold foil
in vacuum.

5. OBSERVATION
• Most of the alpha particles pass straight through
the gold foil without any deflection from their
original path.
• A few alpha particles are deflected through small
angles and few are deflected through large angles.
• A very few alpha particles completely rebound on
hitting the gold foil and turn back on their path.

6. RUTHERFORD MODEL OF AN ATOM
• An atom consist of positively charged, dense and very
small nucleus containing protons and neutrons. The
entire mass of an atom is concentrated in the nucleus.
• The nucleus is surrounded by negatively charged
electrons. The electrons are revolving around the
nucleus in circular paths at very high speed. These
circular paths of the electrons are called orbits.

7. RUTHERFORD MODEL OF AN ATOM
• An atom is electrically neutral because the number of
protons and electrons is equal.
• The size of nucleus is very small as compared to size of
atom.

8. DRAWBACK OF RUTHERFORD MODEL OF AN
ATOM
He does not explain the stability of an atom. In the
Rutherford’s model of an atom, the negatively charged
electron revolves around the positively charged nucleus in
circular path. If an object moves in a circular path, the its
motion is said to be accelerated. This means that motion of
an electron revolving around the nucleus is accelerated. If
a charged particle undergoes accelerated motion, then it
must radiate energy continuously.

9. DRAWBACK OF RUTHERFORD MODEL OF AN
ATOM
Thus, the energy of revolving electron will decrease
gradually, and their speed will also go on decreasing and
ultimately the electrons should fall into the nucleus. This
makes atom very unstable and hence the atom should
collapse.

10. CONCLUSION
Most of the space inside the atom is empty because most of the α-
particles passed through the gold foil without getting deflected. Very few
particles were deflected from their path, indicating that the positive charge of
the atom occupies very little space.

11. FAQ'S
• Name the particle used by Rutherford in his experiment to determine the
structure of an atom?
• State one drawback of Rutherford’s model of an atom?

12. THANK YOU