RUTHERFORD ATOM MODEL

ATOM MODEL

1. RUTHERFORD ATOM
MODEL
(ATOMIC STRUCTURE)
by
M.KANNAN

2. INTRODUCTION
•knowing atomic structure is very important to understand
•elements, their chemical reactions and nuclear reactions too.
We human beings are very inquisitive to know correct
atomic structure. Rutherford conducted a fantastic
experiment to find out atomic structure. Rutherford atom
model gives more or less correct picture of an atom.

3. Alpha
particles
start
Lead
screen
Thin
gold
foil
Fluorescent screen
EXPERIMENT

4. DESCRIPTION
Alpha particles from the polonium sample passed through
lead slit for a narrow beam. Then they passed through thin
gold foil.A t the centre of the fluorescent screen more
scintillations were observed .some were observed little above
and few further above as it is shown in the figure.
Rutherford told positive charge of atom should be contained
at the centre of the atom;only then repulsive force 2Ze*e/r
Newtons (Z is atomic number, e is electron charge and r is
radius of nucleus) could have deflected alpha
particles.Deflection occurred because alpha particles too are
positively charged.

5. THEORY
The fact that more alpha particles went straight shows that there is
more space between electrons and the positively charged nucleus.
The angle of scattering depends upon the factor called ‘impact
parameter.’ closer the approach of alpha particle more the de4flection
was observed.
The impact parameter is given by the factor,b= Ze*e* cot0.5
0 .5mv*v 4
where is angle of scattering,m is mass of alpha particle&v is its
velocity.

6. DEFINITION FOR IMPACT
PARAMETER
Impact parameter(b) is the perpendicular distance between the
velocity vector and centre of the nucleus.
b

7. Conclusion 1
Positive charge of atom is contained at the core called nucleus.

8. CONCLUSION 2
There is more space between positively charged nucleus and
negatively charged electrons.

9. CONCLUSION 3
The negatively charged electrons revolve around the positively
charged nucleus.

10. SUMMARY
Conclusions 1,2 &3 constitute Rutherford Atom Model.

11. EXERCISE
Calculate angle of scattering if alpha particle retraces its path.

12. SOLUTION FOR EXERCISE
b=Ze*ecot0.5
0.5mv*v

Here b= 0
so cot0.5
hence 0.5
and 

13. ALL THE BEST! GOD
BLESS YOU,DEAR
STUDENTS,AS YOU
LEARN
MORE OF HIS
CREATION.