00:01
In this question, we're working out the binding energy and the binding energy pernucleon for a lithium 6 and a lead 208 atom.
00:09
So we'll start the question with lithium 6, which has three protons and three neutrons.
00:19
So to find in binding energy, we add up the constituent parts, the masses of the constituent parts of the atom, and we take away the known mass for the atom.
00:29
And that gives us a mass difference.
00:31
We then convert this mass difference into a.
00:34
Mev, that gives us our binding energy.
00:36
And then to find binding energy per nucleon, we simply divide that number by the number of nucleons.
00:41
So for lithium 6, lithium 6 can be thought of as being made up of three hydrogen atoms, as that is three protons with an electron.
00:54
So three protons, and three neutrons.
00:59
So that's the constituent masses that make up a lithium atom.
01:03
From that we take away the known mass of lithium.
01:08
So i'll just put the numbers in here.
01:10
So the mass of hydrogen atom is 1 .007 -825, and that is in u, atomic mass units.
01:24
Then the mass of a neutron is 1 .008665.
01:33
And finally, the mass of the lithium atom is 6 .015 -121.
01:44
And these are all in u.
01:47
So let's just put that into the calculator and we will get our mass defect.
01:54
So three times 1 .007, 825 plus three times 1 .008 -665 minus 6 .0151.
02:09
And our mass defect is equal to 0 .03439u.
02:17
And then to convert from you to mega electron volts, we times by 931 .5.
02:25
So this answer times by 931 .5 is equal to 32 .0 m .v or 31 .99, however you want to write it.
02:43
So that is our binding energy for lithium.
02:45
And then to find our binding energy per nucleon, we simply do our binding energy, 32 .0, divided by the number of nucleons, which is this top number here, which is six.
02:57
And that gives us an answer of 5 .3m .v.
03:15
So that is part a.
03:17
Done.
03:18
I'll just now clear the board, and we can look at part b...