Grade 9 science - The Atomic Models

1. ATOMIC
MODEL

2. BILLIARD BALL MODEL
JOHN
DALTON

3. JOHN DALTON BASED HIS
ATOMIC THEORY ON
TWO VERIFIED SCIENTIFIC
LAWS: THE LAW OF
CONSERVATION OF MASS
AND THE LAW OF
CONSTANT

4. THE LAW OF CONSERVATION OF MASS WAS
ESTABLISHED BY ANTOINE LAVOISIER. IT
STATES THAT WITHIN A CLOSED SYSTEM,
MATTER CANNOT BE CREATED OR
DESTROYED. IT CAN CHANGE FORMS BUT
IS CONSERVED.

5. THE LAW OF CONSTANT COMPOSITION
WAS FORMULATED BY JOSEPH PROUST.

6. DALTON’S ATOMIC THEORY
1. EVERYTHING IS COMPOSED OF ATOMS,
WHICH ARE THE INDIVISIBLE BUILDING BLOCKS
OF MATTER AND CANNOT BE DESTROYED.
2. ALL ATOMS OF AN ELEMENT ARE IDENTICAL.
3. THE ATOMS OF DIFFERENT ELEMENTS VARY
IN SIZE AND MASS.
4. COMPOUNDS ARE PRODUCED THROUGH
DIFFERENT WHOLE-NUMBER COMBINATIONS
OF ATOMS.
5. A CHEMICAL REACTION RESULTS IN THE
REARRANGEMENT OF ATOMS IN THE
REACTANT AND PRODUCT COMPOUNDS.

7. PLUM-PUDDING
MODEL
- JOSEPH JOHN
THOMSON

8. •CATHODE RAY EXPERIMENT
•Thomson discovered the negatively charged
particles, electrons through his cathode ray
experiment. He noticed a movement in a
tube. He called the movement cathode rays.
The rays moved from the negative end of the
tube to the positive end. He realized that the
rays were made of negatively charged

9. •Based on the result of his
experiment, he came out with a
new atomic model known as
plum-pudding model. It
described that the atom is made
of sphere of positive charges
with negatively charged electron
embedded in it.

11. NUCLEAR
MODEL
-ERNEST
RUTHERFO
RD

12. •GOLD FOIL EXPERIMENT
•Rutherford disproved Sir J.J. Thomson's
model of the atom as a uniformly
distributed substance. Because only very
few of the alpha particles in his beam
were scattered by large angles after
striking the gold foil while most passed
completely through, Rutherford knew
that the gold atom's mass must be

13. GOLD
FOIL
EXPERIME
NT

15. PLANETA
RY
MODEL
- NIELS
BOHR

17. •Electrons have a definite energy in each orbit, which
increases as the distance of orbit from nucleus
increases.
•There is no absorption or emission of energy if the
electron stays in its orbit. However, when an electron
absorbs extra energy, this electron moves to a higher
energy level. This when we say that the electron
becomes excited making the atom unstable. If an
excited electron jumps down a level, it loses energy.
The energy the electron loses becomes light with a
frequency corresponding to a change in energy.

18. QUANTUM
MECHANICAL
THEORY
- ERWIN
SCHRODINGER

19. •These three physicists led the development of a
better model of atom.
• Louie de Broglie proposed that electron could be
a wave.
• Erwin Schrodinger formulated a mathematical
equation to describe the hydrogen atom. This
equation leads to the model of quantum
mechanical.
•Werner Karl Heisenberg discovered that the

20. •The quantum mechanical model shows
that atom has a nucleus at the center
surrounded by the moving electrons. The
electrons are described as a cloud of
negative charge with a geometric shape.
These electrons are arranged in principal
or main energy levels also called as shells
that consist of one or more sublevels.

21. ELECTRON CONFIGURATION IS
THE WAY WHICH ELECTRONS
ARE ARRANGED IN THE
ELECTRON SHELLS OF THE
ATOM. ELECTRONS ALWAYS
FILL THE ELECTRONS SHELLS
WITH LOWER ENERGY FIRST.