Calculating Binding Energy (OCR A Level Physics): Revision Note
Exam code: H556
Calculating Binding Energy
Binding energy can be calculated using the equation:
ΔE = c2Δm
Where Δm is the mass defect of a nucleus
This can be calculated using:
Δm = Zmp + (A – Z)mn – mtotal
Where:
Z = proton number
A = nucleon number
mp = mass of a proton (kg)
mn = mass of a neutron (kg)
mtotal = measured mass of the nucleus (kg)
Worked Example
Answer:
Step 1: Calculate the mass defect
Number of protons, Z = 26
Number of neutrons, A – Z = 56 – 26 = 30
Mass defect, Δm = Zmp + (A – Z)mn – mtotal
Δm = (26 × 1.673 × 10-27) + (30 × 1.675 × 10-27) – (9.288 × 10-26)
Δm = 8.680 × 10-28 kg
Step 2: Calculate the binding energy of the nucleus
Binding energy, ΔE = c2Δm
E = (8.680 × 10-28) × (3.00 × 108)2 = 7.812 × 10-11 J
Step 3: Calculate the binding energy per nucleon
Step 4: Convert to MeV
J → eV: divide by 1.6 × 10-19
eV → MeV: divide by 106
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