This power point presentation is created for Science 8 learners. This presentation tackles on the three sub atomic particles of atom, the one who discovers them, how do they discover them and the different atomic theory models.

1. Lesson 2:
Subatomic Particles
RONNIE M. ABSALON, JR
Science Teacher

2. The three subatomic particles of atom
are protons, neutrons and gluons.

3. Atomic Number (Z) is the number of
protons in an atom.

4. Atomic Mass (A) is the sum of protons
and neutrons.

5. The number of electrons in a neutral
atom is equal to the number of protons.

6. What do you think is
our topic for today?

7. What is an atom?
Smallest unit into which matter can be
divided without the release of
electrically charged particles. It
also is the smallest unit of matter that
has the characteristic properties of a
chemical element. As such, the atom is
the basic building block of
chemistry.

8. ELECTRON
NEUTRON
PROTON
SUB-ATOMIC PARTICLES

9. The ELECTRONwas
discovered in 1897 by the English
physicist J.J. Thomson during
investigations of cathode rays. His
discovery of electrons, which he
initially called CORPUSCLES, played a
pivotal role in revolutionizing
knowledge of atomic structure.
Discovering the ELECTRON

10. Lightest stable subatomic
particle known. It carries a
negative charge of
1.602176634 ×
10−19 coulomb, which is
considered the basic unit
of electric charge.
ELECTRON

11. Discovering PROTONS
ERNEST RUTHERFORD is known for
his pioneering studies of radioactivity
and the atom. He discovered that there
are two types of radiation, ALPHA and
BETAparticles, coming from uranium.
He found that the atom consists mostly
of empty space, with its mass
concentrated in a central positively
charged nucleus.

12. PROTON, stable subatomic
particle that has a positive
charge equal in magnitude to
a unit of electron charge and
a rest mass of 1.67262 × 10
−27 kg, which is 1,836 times
the mass of an electron.
PROTON

13. Discovering NEUTRON
SIR JAMES CHADWICK, (20
October 1891 – 24 July 1974) was a
British physicist who was
awarded the 1935 Nobel Prize in
Physics for his discovery of the
neutron in 1932.

14. NEUTRON
The NEUTRON is a
subatomic particle,
symbol n or n 0, with no
net electric charge and a
mass slightly greater than
that of a proton.

16. Performance Task:
“The big difference”
Objectives:
After performing this activity, you should be
able to:
1. compare the masses of the subatomic
particles using different ways of visual
representation
2. infer which subatomic particle contributes
to the mass of the atom

17. Procedure:
1. Refer to the masses of the subatomic particles in Table 2.
Arrange the subatomic particles in increasing mass.
 Q1. Which subatomic particle is the lightest?
 Q2. Which subatomic particle is the heaviest?
 Q3. Which subatomic particles have almost the same mass?

18. Greek philosopher, born in Sicily.
He taught that the universe is
composed of FIRE, AIR, WATER,
AND EARTH, which mingle and
separate under the influence of
the opposing principles of LOVE
and STRIFE.
Early Theories of Matter

19. 500 BC: Democritus & Leucippus
 inferred that all matter is
composed of small, indestructible
particles (indivisible) he named
atomos.
 He taught that there was an infinite
number of them, and that atoms
differed in their size, shape, and
weight.
 He also thought that different
substances were made up of
different kinds of atoms.

20. 460 BC: Aristotle
 He didn't believe in
atoms which are
indivisible but rather
it an be divided
infinitely into smaller
pieces.

21. Dalton’s Atomic Theory
1. Matter is composed of tiny, indivisible
spheres called atoms.
2. Atoms of the same element are
identical, but atoms of one element are
different from those other elements.
Each element has unique atoms.
3. Atoms cannot be created nor destroyed
during a chemical change rather, they
are rearranged to form a new
compounds.
4. Atoms of different elements combine in
simple whole number ratios to form
compounds.
1803: John Dalton

22. 1890-1898: Joseph John
Thomson
 Thomson played around
with radioactive waves
and discovered that atoms
have electrical charges.
 He discovered that those
charges come from small
particles which make up
part of the atom. He
called the particles
electrons.

23. PLUM PUDDING MODEL
 Thomson thought that
atoms consisted of
positively-charged main
bodies, and attached to
these were the
negatively-charged
electrons (plum pudding
model).
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24. Gold-Foil Experiment Testing…

27. Performance Task
“Alpha particle scattering Experiment”
Objectives:
After performing this activity, you should be able
to simulate and describe Rutherford’s model of
the atom
Materials Needed:
 one piece of 25 centavo coin
 paper, any small piece will do
 smooth, clean table, counter or floor

28. Procedure:
1. Tear 20, very small pieces of paper, the size of
mongo beans.
2. Scatter the pieces in a circle on the floor, about
one foot in diameter. Imagine these to be the
electrons in the Thomson’s raisin bread model of the
atom.
3. As forcefully as you can, slide the coin to hit the
circle of paper pieces. Imagine the coin to be the
high speed alpha particle in Rutherford’s experiment.
 Q1. What do you observe? What happened to the
coin?

29. Performance Task
“Rutherford’s Experiment”
Procedure:
1. Refer to Figure 3. Using this
schematic representation of the atoms
of the gold foil, draw the path of the
positively-charged alpha particles as
they move through the atoms.
 Q1. What happens to a positively-
charged alpha particle that comes
near the positively-charged nucleus?
 Q2. What happens when the
positively-charged alpha particle
directly hits the positively-charged
nucleus?

30. Performance Task
“Rutherford’s Experiment”
Q1. What happens to a positively-charged alpha
particle that comes near the positively-charged
nucleus?
 Possible Answer: It will be repelled causing the positively-
charged alpha particle to move at an angle away from the
positively-charged nucleus.
 Q2. What happens when the positively-
charged alpha particle directly hits the
positively-charged nucleus?
 Possible Answer: It will be repelled but the repulsion will be
stronger compared to the repulsion when the positively-
charged alpha particle only came close to the positively-
charged nucleus. The alpha particle will be more strongly
deflected since it hits a particle with a bigger mass, the
nucleus of the gold atom.

31. What kind of experiment
did Rutherford’s perform?
Ernest Rutherford performed an alpha scattering
experiment. He bombarded α-particles on a gold
sheet and then studied the trajectory of these α-
particles.

32. 1909-1911: Ernest Rutherford
 A student of Thomson, designed
a very famous experiment that
proved that the atom is mostly
empty space.
 He bombarded a very thin piece
of gold leaf with alpha particles.
 Where some alpha particles were
reflected, most passed through,
proving that a dense nucleus was
at the center of the atom, but
not much else.
You may access
http://phet.colorado.edu/en/simulation/rutherford-
scattering* for a simulation of Thomson’s plum pudding
model and Rutherford’s alpha scattering experiment.

33. https://phet.colorado.edu/sims/html/rutherford-scattering/latest/rutherford-scattering_en.html

34. What was the primary observation
of Rutherford’s atomic model?
Rutherford observed that
a microscopic positively
charged particle is
present inside the atom,
and most of the mass of
an atom is concentrated
over there.

35. Gold-Foil Experiment Observations
Nuclear Model

36. Gold-Foil Experiment Observations
Nuclear Model

37. Gold-Foil Experiment Observations
Nuclear Model

38. Gold-Foil Experiment Observations
Nuclear Model

39. Analogy…

40. Rutherford Atomic Model
 The positive charge and most of the mass of an atom is
concentrated in an extremely small volume. He called
this region of the atom as a nucleus.
 Rutherford’s model proposed that the negatively
charged electrons surround the nucleus of an atom. The
electrons surrounding the nucleus revolve around it
with very high speed in circular paths. He named these
circular paths as orbits.
 Electrons being negatively charged and nucleus being a
densely concentrated mass of positively charged
particles are held together by a strong electrostatic
force of attraction.

41. 1912-1913: Niels Bohr
 Bohr improved Rutherford’s
model by noticing that energy
levels in atoms went up and
down by specific, “pre-set”
amounts.
 He suggested that electrons
move around the nucleus of an
atom like planets around the
sun, and that they move from
orbit to orbit as they gain and
lose energy.

42.  Bohr explained that the
electrons in an atom move
around the nucleus in regions
called electron shells or
energy levels which move
with enough energy to remain
in their orbits.

43. 1916: Bohr – Arnold
Johannes Wilhelm
Sommerfeld’s Model
 AJW Sommerfeld
modified Bohr model,
placing electrons in
elliptical orbits.

44. 1920-present: Quantum Model /
Particle-Wave models
-Erwin Schrodinger and other
scientists
 They showed that electrons
form negatively charged
clouds around the nucleus. It
is impossible to determine
exactly where an electron is
at any given time.

45.  There are three subatomic particles — protons,
electrons and neutrons — and they are arranged in
the currently accepted model of the atom.
 Among these subatomic particles, it is the number
of protons that identify the atoms of an element.
All atoms of an element contain the same number
of protons in their nuclei. This number is the
element’s atomic number.
 In the next activity, you will refer to the periodic
table in determining the atomic number.
Notice that no two elements have the same
atomic number.