Structure of Matter
Two years of Physics in one hour

A lump of coal

Mass is the ability of an
object to resist acceleration
Force = mass x acceleration

Mass is also the force
felt from gravity (weight)

Coal is made of Carbon atoms

Mass = 2×10-29 kg
≡12 amu

How much force is needed to
accelerate a carbon atom to
Mass of Carbon Atom: 2×10-26kg
Speed of light: 3×108 meters/sec (m/s)
Acceleration = Δv/Δt= 3×108 m/sec/sec
(m/s2)
Force = m a = 2×10-26kg × 3×108 m/s2

Objects are made out of atoms
Mass is the ability to resist acceleration
Scientific notation lets us work with the very large and very small

The nucleus is very small
–
–
+ +

Frequency = number of cycles per sec

O shell
N shell
M shell
L shell
Pauli Exclusion principle:
at most two electrons in each level
K shell

Energy of
emitted photon 1 neV 1µeV 1meV 1eV 1keV 1MeV 1GeV
(eV)

Objects are made out of atoms
Mass is the ability to resist acceleration
Scientific notation lets us work with the very large and very small
Electrons on the outsides of atoms give all the chemical properties
Electrons live in standing wave states each with a particular energy/
frequency
No more than two electrons in each state
Putting energy into an atom can raise an electron to a high state
An electron falling to a low state releases a characteristic photon
with a defined energy
With massive atoms, these characteristic photons can be in the 100
keV medical interest range.

A=Z+N
Symbol also gives
12
6C6 number of protons
Z: number of protons
N: number of neutrons

Nuclear Shell Model
pnpnpnpnpnpn
pnpnpnpnpnpn
pnpn
pnpnpnpn
pnpn

Nuclear Shell Model
• Nuclei should have about pppppp
the same number of
protons and neutrons
pppppp
pnpnpnpnpnpn
pnpn
pnpnpnpn
pnpn

Nuclear Shell Model
• Nuclei should have about
the same number of
protons and neutrons pnpnpnpnpnpn
• Nuclei with magic numbers pnpnpnpnpnpn
of protons or neutrons are
more stable
pnpn
• Nuclei with even numbers pnpnpnpn
of protons and neutrons
are more stable
pnpn

Nuclear Shell Model
• Nuclei should have about n
the same number of
protons and neutrons pnpnpnpnpnp
• Nuclei with magic numbers pnpnpnpnpnpn
of protons or neutrons are
more stable
pnpn
• Nuclei with even numbers pnpnpnpn
of protons and neutrons
are more stable
pnpn
• Nuclei can be excited

Heavy nuclei tend to have
more neutrons than protons

–
–
+ +

Nucleus is held together
by “Strong Force”
Strong force must be
stronger than
electric repulsion
between protons
Neutrons and
protons both make
strong force

Is the mass of a nucleus
the sum of its parts?
+ + m=1.0073×2
m=1.0087×2 m=4.0026
total=4.0320 amu difference = .0302 amu

Attraction between neighboring nuclei
Surface tension
Repulsion between positive protons
Same number of protons as neutrons

Objects are made out of atoms
Mass is the ability to resist acceleration
Scientific notation lets us work with the very large and very small
Electrons on the outsides of atoms give all the chemical properties
Electrons live in standing wave states each with a particular energy/
frequency
No more than two electrons in each state
Putting energy into an atom can raise an electron to a high state
An electron falling to a low state releases a characteristic photon
with a defined energy
With massive atoms, these characteristic photons can be in the 100
keV medical interest range.
Z=protons, N=neutrons, A=N+Z, 12C has 6 neutrons, 14C has 8.
Shell model explains why N≳Z, shell bands
Strong force holds nuclei together
Nuclei have less mass than constituent protons and neutrons. The
difference is the binding energy.
Liquid drop model part of semi empirical mass formula, explains
binding energy with contributions from strong force interactions,
surface tension, electric repulsion from protons, N~Z

Objects are made out of atoms
Mass is the ability to resist acceleration
Scientific notation lets us work with the very large and very small
Electrons on the outsides of atoms give all the chemical properties
Electrons live in standing wave states each with a particular energy/
frequency
No more than two electrons in each state
Putting energy into an atom can raise an electron to a high state
An electron falling to a low state releases a characteristic photon
with a defined energy
With massive atoms, these characteristic photons can be in the 100
keV medical interest range.
Z=protons, N=neutrons, A=N+Z, 12C has 6 neutrons, 14C has 8.
Shell model explains why N≳Z, shell bands
Strong force holds nuclei together
Nuclei have less mass than constituent protons and neutrons. The
difference is the binding energy.
Liquid drop model part of semi empirical mass formula, explains
binding energy with contributions from strong force interactions,
surface tension, electric repulsion from protons, N~Z