 What
is an istope?
 What makes an isotope different than its
element?
5/2/12 
• Describe nuclear reactions
and perform balancing of
nuclear reactions by solving
problems.
• Apply radioactivity
equations by solving
problems.
 Atomic
nuclei having the same number of
protons but different number of neutrons
Nuclear
reaction: A reaction in
which the number of protons or
neutrons in the nucleus of an atom
changes.
 Atomic number: Number of protons
in the nucleus of the atom
Mass number: Sum of protons and
neutrons in the nucleus of the atom
Radioactive
decay
process in which the
nucleus of an atom
emits an alpha
particle
Nucleus
a helium
atom
of
Radioactive
decay that
occurs when a neutron is
changed to a proton within
the nucleus of an atom, and a
beta particle and an
antineutrino are emitted
Radioactive
process of decay
that takes place when the
nucleus of an atom emits a
gamma ray.
 http://library.thinkquest.org/17940/t
exts/radioactivity/radioactivity.html

The difference between the sum of the mass of the
individual nucleon (proton or neutron) and the actual mass.


Z m  m 
p
e

m  matom  


(A

Z)m

n 
Fermium-253 has a half-life of
0.334 seconds. A radioactive
sample is considered to be
completely decayed after 10
half-lives. How much time will
elapse for this sample to be
considered gone?
E binding 
(massdefect(inu))(931.49MeV /u)
 The
energy equivalent of the mass
defect; it is always negative
 It
is the minimum amount of energy needed to
break the nucleus into its component nucleons.
The
half life of Zn-71 is
2.4 minute. If one had
100 g at the beginning,
what is the decay rate of
Zn-71?
m  m0e
 m=mass
remaining
 Original mass
 t
The
half life of Zn-71 is 2.4
minute. If one had 100 g at
the beginning, how many
grams would be left after
7.2 minutes elapsed?
Use
the rest of class
to work on the paper:
Radioactivity;
problems: #2,5,6, and
7
 Pd-100
has a half-life of 3.6 days. If one
had 6.02x1023 atoms at the start, how
many atoms would be present
 When
an electron and a positron collide,
the two can annihilate each other,
resulting in energy in the form of gamma
rays. In this process, called annihilation,
matter is converted directly into energy.
The inverse of annihilation can also occur
where energy is converted directly into
matter. The inverse of annihilation is
called pair production.
 explains
what the world is and what holds
it together.
 explains all the hundreds of particles and
complex interactions.
 made up of
• Quarks
• Leptons
• Force carriers
 Six
flavors (three pairs):
up/down, charm/strange,
and top/bottom.
 for each of these quarks,
there is a corresponding
antiquark.
 fractional electric
charge, unlike the proton
and electron, which have
integer charges of +1
and -1 respectively.
 Quarks also carry
another type of charge
called color charge.
 Composite
particles made of quarks
 individual quarks have fractional
electrical charges, so hadrons have a net
integer electric charge.
 no net color charge even though the
quarks themselves carry color charge
 Two classes
 ...are
any hadron which is made of three
quarks (qqq).
 Because
they are made of two up quarks
and one down quark (uud), protons are
baryons. So are neutrons (udd).
 ...contain
 Ex: pion
one quark (q) and one antiquark.
(π+), which is made of an up quark
and a down anitiquark.
 an antipion (π-) is made up a down quark
and an up antiquark.
 a meson consists of a particle and an
antiparticle, so it is very unstable.
 six
leptons; three have electrical charge
and three do not.
 The three charged leptons are the
electron (e-), muon() and the tau(),
 Three types of neutrinos (). They have no
electrical charge, very little mass, and
are hard to find.
 For each lepton there is a corresponding
antimatter antilepton.
 anti-electron = the "positron.”
 Quarks
are sociable; only exist in composite
particles with other quarks
 leptons are solitary particles.
 charged leptons as independent cats with
associated neutrino fleas, which are hard to
see.
U-238
has a half-life of
9
4.46x10 years. How much U238 should be present in a
sample 2.5 x10 10 years old, if
2 grams were present
initially?