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Atomic Structure
Basic and Beyond
What are the 3 major parts of an
atom?
Protons
Electrons
Neutrons
Where is each located?
What are the charges on each
basic part?
The Nucleus
The nucleus is the central part of an atom.
It is composed of protons and neutrons.
Unlike in a living cell, the nucleus of an
atom is not a physical thing.
It is the name for the area that holds
the protons and neutrons.
The nucleus contains most of an atom's
mass. Why?
What forces hold the atom
together?
Electromagnetic
Strong Force
likes repel,
opposites attract (+ or -)
interacts with hadrons
or nucleons so the protons
and neutrons
binds them together
works only at distances
smaller than 1
quadrillionth of a meter!!!
Weak Force
·works with quarks and
leptons and decides
how flavors change
·helps stabilize nuclei
through beta decay
·shorter distances than
the strong force!
Gravity
Since this binds matter
together based on mass,
we think this plays no role
in atoms
Protons
Protons are positively charged particles
found in the atomic nucleus.
Protons were discovered by Ernest Rutherford.
Protons have a mass.
We designate this mass as 1 amu
(atomic mass unit).
Protons determine the atomic number and thus
the identity of the substance.
Who discovered the proton? What experiment did
he use?
Can protons be broken down?
Experiments done in
the late 1960's and
early 1970's
showed that protons
are made from
other particles
called quarks.
Protons are made from
two 'up' quarks and
one 'down' quark.
What is a quark, anyway?
Fundamental particle which
possesses electric charge
and 'strong' charge.
They combine in groups of
two or three to form
mesons and baryons
The are held together
by the strong force.
There are several kinds of
quarks
Quarks come in six
different species
(physicists call them
'flavors')
Each flavor has a
unique mass.
Quark song:
http://www.youtube.com/watch?v
=U0kXkWXSXRA
Neutrons
Neutrons are uncharged particles
found in the atomic nucleus.
They have a mass of 1 amu
Isotopes result when neutron number changes
The decimals in the atomic mass are from
the AVERAGE of the isotopes.
Neutrons were discovered by
James Chadwick in 1932.
Why would a neutron be hard to discover?
Isotopes
Example:
Can Neutrons Be Broken
Down?
• Experiments done in
the late 1960's and
early 1970's showed
that neutrons are
made from other
particles called
quarks. Neutrons are
made from one 'up'
quark and two 'down'
quarks.
What is the Electron Cloud Model?
Diagram 1:
Electrons
Electrons are negatively charged particles
that surround the atom's nucleus.
The mass of an electron is so small
that it is called “zero”.
Electrons determine chemical properties
of the atom.
Electrons are arranged in orbitals
that are part of probability clouds.
Who discovered electrons? What experiment
was used? Why were they easy to discover?
So subatomic particles are
themselves made of smaller
particles!
• Subatomic particles composed of fast
moving points of energy called quarks
Quark Calculations
(for protons and neutrons)
Each proton is 2 up quarks and 1 down quark
2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1
Each neutron is 2 down quarks and 1 up quark
2(-1/3) + 2/3 = 0
So, are there other
characteristics of quarks?
The two lightest are
'up' and 'down' quarks
They combine to form
protons and neutrons.
The heavier quarks aren't
found in nature and have
so far only been observed
in particle accelerators.
Can we get smaller?
Fermions
Bosons
Leptons
Hadrons
And more
So we can categorize
And get smaller
But quarks are still the
smallest for now
Can things get even smaller?
Higgs boson
Neutrino
And more are
hypothesized sub sub
sub particles!
Still looking for evidence
for these. . .
Why are sub subatomic
particles important?
Predict properties such as
nuclear decay
Explain types of
nuclear decay
Help us to understand
organization of matter
Could lead to many
things in the future:
energy, new elements
How do accelerators work?
How are new particles
discovered?
http://www.youtube.com/watch?v=V0KjXs
GRvoA