CLASS COPY
9th Grade Physical Science
Unit 5: The Power of the Nucleus
The Real Fundamental Particles
Fundamental particles are the smallest particles that make up matter and are responsible for the
fundamental forces of the universe. Atoms are not the most fundamental particle. We know atoms are
made of Protons, Neutrons, and Electrons. Scientists used to think that these three sub-atomic particles,
protons, neutrons and electrons, were fundamental particles that made up all matter.
No! Protons and Neutrons are not fundamental particles! They are made of even smaller particles.
This is the current list of fundamental particles (let’s see if this is still true 50 years from now!):
Types of Fundamental Particles
Quarks
Leptons
Force Carrier particles
6 types
6 types
6 types
# of different types
of each particle
All have a partial charge •3 have negative charge •4 have no charge (3 of these
Charge on
(+ or -)
•3 have 0 charge; are
also have no mass)
particles
(either 1/3 or 2/3 charge) named “neutrinos”
•2 have a charge
Mass of particles
Mass varies.
Mass varies.
The neutrinos have
almost no mass!!
Purpose/fun facts
Quarks exist in groups.
These groups make up
protons and neutrons
•Leptons are solitary
particles
• Electrons are a type of
lepton
Useful information about particles and their names:
A hadron is a group of 3 quarks.
A proton is a hadron and a neutron is a hadron.
A proton is made of 2 up quarks and 1 down quark.
A neutron is made of 2 down quarks and 1 up quark.
An electron is a lepton that is always with its neutrino.
A gluon is a force carrier particle that holds quarks together.
The gluons make up the strong force.
There are also positrons, anti-neutrinos, muons, and tauons and more!
•1 has mass and no charge
•2 have mass AND a charge
•3 have no mass
These carry the fundamental
forces (gravity, strong force
and electromagnetic force)
that allow of matter to
interact with each other.
A Silly Way to Remember some of the
Fundamental Particles
Quark
Quark
UP
DOWN
Charge:
+ 2/3
Quark
Charge:
- 1/3
Quark
STRANGE
Charge:
+ 2/3
Quark
CHARM
Charge:
- 1/3
Quark
BOTTOM
Charge:
+ 2/3
TOP
Charge:
- 1/3
Lepton
ELECTRON
e-
Force Carrier particle
PHOTON
Lepton
Charge:
0
Charge:
-1
00
ELECTRON NEUTRINO
Force Carrier particle
GLUON
The Strong Force
We have another problem with atoms, though. What binds the nucleus together?
The nucleus of an atom consists of a bunch of protons and neutrons crammed together.
Since neutrons have no charge and the positively-charged protons repel one another,
why doesn't the nucleus blow apart?
We cannot account for the nucleus staying together with
just electromagnetic force. What else could there be? Gravity? Nope! The
gravitational force is far too weak to overpower the electrostatic force.
So how can we account for this dilemma?
The strong force holds quarks together to form hadrons, so its force carrier particles are whimsically
called gluons because they so tightly "glue" quarks together.
The strong force only takes place on the really small distances of quark interactions, which is why you are
not aware of the strong force in your everyday life.
So now we know that the strong force binds quarks together to form a hadron (such as a proton or a
neutron). But that still does not explain what holds the nucleus together, since positive protons should
repel each other through their electrostatic force.
So what holds the nucleus together? Huh?
The answer is that, in short, they don't call it the strong force for nothing. The strong force between the
quarks in one proton and the quarks in another proton is strong enough to overwhelm the repulsive
electromagnetic force.
Strong Force is stronger than Electrostatic Force. Both are ESSENTIAL for holding an atom
together and holding groups of atoms together to form molecules!!!!