Binding Energy

1
Binding Energy
2
Basic Terminology
nucleon
nuclide
atomic number Z atomic mass number A
isotope
A X Z
3
Atomic size 10-10 m
angstrom A
number of atoms on surface of a coin, 1 cm in
diameter?
1016
4
Masses on periodic table based on
carbon-12 atom mass 12.0000
atomic mass units (u)
6 protons 6 neutrons 6 electrons

6 x 1.007276 u
6 x 1.008665 u
6 x 0.00054858 u
total mass 12.098937 u
mass defect 0.098937 u
5
Mass defect converted to energy called the
binding energy
1 u of mass 1.66054 x 10-27 kg E mc2 (1
u)(c2) 931.5 MeV
Conversion factor 1 u 931.5
MeV/c2
6
binding energy of C-12
92.16 MeV
Binding energy is the energy the atom lacks
the energy needed to split the atom apart
7
(No Transcript)
8
Determine the binding energy of He-4.
2 p 2 x 1.007276 u 2.014552 u 2 n
2 x 1.008665 u 2.017330 u 2 e 2 x
0.00054858 u 0.00109716 u
total mass 4.032979 u
mass of He-4 atom 4.002602 u
mass defect 0.030377 u
BE 28.30 MeV
9
A nucleon (p or n0) inside a nucleus has less
mass than its mass outside the nucleus.
Missing mass converted to energy.
10
Average Binding Energy/nucleon
BE/A
helium 4 28.30/4 7.1 MeV
The greater the BE/A, the more tightly the
nucleus is held together.
11
Nuclei below Fe fusion Nuclei above Fe fission
12
Any nuclear transformation that moves nuclei
toward iron releases energy.
13
Determine BE/nucleon for Fe-56
26 H-1 26 x 1.007825 30 n 30 x 1.0086665
56.4635 u
Fe-56 55.9349 u
?m 0.5286 u
BE 492.4 MeV
BE/A 8.8 MeV
14
Reactants ? Products Energy
To yield energy, products must have less mass
than reactants.
If products have more mass, energy must be added.
15
n
KEproducts
KEreactants
energy equivalent of mass decrease in the
reaction