Grigoriy S. answered • 12/04/21

AP Physics / Math Expert Teacher With 40 Years of Proven Success

As we know, the total mass of a stable nucleus is always less than the sum of the masses of its separate protons and neutrons. The ** difference** between them is called

**. When it is destroyed, it is converted to the so-called**

*mass defect***of the nucleus. It means that to find binding energy we need:**

*binding energy*1. Find the total mass of all neutrons and protons in a nucleus.

2. Subtract from it the mass of a stable nucleus.

3. Express this difference in units of energy.

_{3}Li^{9} has 3 protons and 6 (9 – 3) neutrons.

The mass of the proton in atomic mass units m_{p} = 1.00728 u, mass of the neutron m_{n}= 1.008665 u.

The mass of all protons is 3 x 1.00728 u = 3.02184 u.

The mass of all neutrons is 6 x 1.008665 u = 6.05199 u.

Then the total mass of all particles in Li nucleus is 3.02184 u + 6.05199 u = ** 9.07383 u**.

Now we subtract from this mass the mass of the Li nucleus ** 9.026789 u**.

The difference will be ** Δm** = 9.07383 u – 9.026789 u =

**.**

*0.047041 u*And finally, knowing that if the mass is changing by ** 1 u **the released energy is

**, we find that the**

*931.5 Mev***binding energy for lithium is 43.81869 Mev**.