Download Nuclear Physics and Radioactivity

Nuclear Physics
Vocabulary
alpha particle - positively charged particle consisting of two protons and
two neutrons. (Helium nucleus)
atomic mass number (A) - the number of protons and neutrons in the
nucleus of an atom.
atomic mass unit - the unit of mass equal to 1/12 the mass of a carbon-12
nucleus; the atomic mass rounded to the nearest whole number is called the
mass number.
atomic number (Z) - the number of protons in the nucleus of an atom.
beta particle - high speed electron emitted from a radioactive element
when a neutron.
decays into a proton
binding energy - the nuclear energy that binds protons and neutrons in
the nucleus of the atom.
element - a substance made of only one kind of atom.
isotope - a form of an element which has a particular number of neutrons,
that is, has the same atomic number but a different mass number than the
other elements which occupy the same place on the periodic table.
Vocabulary
mass defect - the mass equivalent of the binding energy in the nucleus of
an atom by E = mc2
neutron - an electrically neutral subatomic particle found in the nucleus of
an atom
nuclear reaction - any process in the nucleus of an atom that causes the
number of protons and/or neutrons to change
nucleons - protons or neutrons
strong nuclear force - the force that binds protons and neutrons together
in the nucleus of an atom
transmutation - the changing of one element into another by a loss of
gain of one or more protons
Equations, symbols and units
E  mc
2
A
Z
Three units for mass :
1u  1.661x1027 kg  931.5 MeVc 2
where
E = binding energy of the nucleus
Δm = mass defect of the nucleus
c = speed of light = 3 x 108 m/s
u = atomic mass unit
X = element symbol
A = atomic mass number (number of protons and
neutrons)
Z = atomic number (number of protons)
X
Find the number of protons, electrons and
neutrons in a neutral atom of iron.
# protons + #neutrons
56
26
Fe
# protons
26 protons
30 neutrons
neutral → #protons = # electrons = 26
Before
M1
After
M2
M3
Eo <=
Mo >
=
Ef
Mf
Eo = Ef + (Mo-Mf)c2
Eo = Ef + (Δm)c2
MASS is transferred to ENERGY
14
7
N
n n n
n n n n p
p p p p p p
14
7
N
n n n
n n n n p
p p p p p p
Mass defect is responsible for the binding energy.
Ebinding = (Δm)c2
Transmutation of nitrogen into carbon
14
7
Nuclide/particle
N n C 
1
0
14
6
14
N
neutron
14
C
proton


Mass (u)
14.0031
1.008664
14.003241
1.007825
Nuclear fusion – The joining of two small
nuclei to form one big one.
Nuclear fission – Splitting a large nuclei to
two smaller nuclei.
Binding energy per nucleon vs. mass number
Binding energy
Per nucleon
(MeV)
Mass number
 
 

Fusion Examples:
Nuclide
1
H
2
H
3
H
3
He
4
He
1
0
n
Mass (u)
1.007825
2.014101
3.016049
3.016029
4.002603
1.008664



2
1
3
1
4
2
1
0
H H He n
2
1
3
2
1
0
2
1
3
1
H H He n
2
1
2
1
2
1
1
1
H H H p
3
2
4
2
1
1
H He He p
Fission Example:
If 236U splits into 100 Mo and 126 Sn , how many
neutrons will be produced? Calculate the energy
released in this reaction.
Z
92
42
50


symbol
U
Mo
Sn
A
236
100
126
Mass (u)
236.045563
99.907476
125.907653