How Is the Mass Defect of the 7Li Nucleus Calculated?

[dvolpe]

Homework Statement

What is the mass defect of the 7Li nucleus (A = 7)?

Homework Equations

mass of 7Li nucleus per atomic table is 7.016004 u
N = A-Z or #neutrons = 7-3 = 4
computed mass of proton and neutrons in nucleus = 3 p*mass of p + 4n *mass of n
mass of proton = 1.00726 u
mass of neutron = 1.008665 u

mass defect = computed mass of protons + neutron - (atomic mass of nucleus per table)

The Attempt at a Solution

computed mass of p + n = 3(1.00726 u) + 4(1.008665 u) = 7.05644 u
mass defect of nucleus = 7.05644 - 7.016004 = .040436 u

Answer is .0421...help!

 

[anathema]

Hello! Your attempt at solving this problem is correct. The slight difference in the answer may be due to rounding errors in the atomic masses of protons and neutrons. The more accurate value for the mass defect of the 7Li nucleus is actually 0.040436 u, as you have calculated. So you were correct in your solution! Keep up the good work.