In nucleous the nucleon’s are bound together by a short range ,strogly attractive force called “nuclear force”.
In order to decompose a nucleus in to its constituent nucleus .Some energy is required this energy is called Nuclear Binding energy .
“The mass of nucleons always remains greater than the mass of nucleous ”.
The difference of masses is called mass defect ( m ) .
The energy equivalent to mass defect is called nuclear binding energy .
Let Mp ——– mass of proton.
Mn ——– mass of one neutron.
Z ———- no of proton .
N ———- (A –Z ) is no of neutrons .
MN ——– mass of nucleus .
Mass defect = mass of nucleus +(mass of protons + mass of neutrons)
m =[ ZMp + (A – Z)Mn – MN ]
Now , the average energy required to remove one nucleon from nucleus is called average binding energy .
EB
A
Average binding curve
A graph between average binding energy per nucleons and mass number ois called average binding energy curve .
From average binding energy curve we note that —–
- Average binding energy of all nuclei +ve its energy is used in forming nucleus .
- Average binding energy for nucleus of light nuclei such as 1H , 1H2 , etc is very small .
- For nuclei A average bindning energy curveshows peaks for some nuclei such as 2He4 ,4Be , etc .( having equal number of protons & neutrones )
This indicates that these nuclei are more stable than their neighbour .
- For nuclei mass no 20 to 180 the average binding energy per nucleus is almost constant for Fe56 it is maximum (8.8MeV) .it indicates that these nuclear almost equally .
- For nuclei A>120 the average binding energy per nucleon’s rapidly decreases and 7.6 MeV for Uranium . It is due to increase in elecrostastic force of repulsion between protons as their number increase with increasing mass nuclear .
- For nuclei havier than Uranium the nuclei becomes unstable because the number of protons increase and also the electrostatic force of repulsion between them.
The substsnce becomes radioactive .
Importance of average binding energy
- The binding energy per nucleons is +ve for all nuclei ,it means the energy is used to form nuclie .
- The average binding energy per nucleons is very small such 1H1 ,1H2 etc . So these nuclei can be combined to form a heavy nuclei [Nuclear Fusion ] . The average binding energy is also small .Such Uranium those nuclei can be breakup in to some light nuclei [Nuclear Fission ]