What is the mass defect of lithium? Assume the following:

Question

Atomic number of lithium = 3
Atomic mass of lithium = 7.0144 atomic mass units.
Mass of 1 proton = 1.0073 atomic mass units.
Mass of 1 neutron = 1.0087 atomic mass units.
A.
0.0043 atomic mass units
B.
0.0423 atomic mass units
C.
3.0219 atomic mass units
D.
4.0348 atomic mass units
E.
7.0567 atomic mass units

Answer 1

To calculate the mass defect of lithium, we can follow these steps:

1. Determine the number of protons and neutrons in lithium:

   • The atomic number of lithium is 3, which means it has 3 protons.
   • Since the atomic mass of lithium is approximately 7, we can estimate the number of neutrons by subtracting the number of protons from the atomic mass: $$\text{Number of neutrons}=\text{Atomic mass}-\text{Number of protons}=7-3=4$$

2. Calculate the mass of the nucleons (protons and neutrons):

   • Mass from protons: $$\text{Mass of protons}=(\text{Number of protons})\times (\text{Mass of 1 proton})=3\times 1.0073=3.0219\text{ atomic mass units}$$
   • Mass from neutrons: $$\text{Mass of neutrons}=(\text{Number of neutrons})\times (\text{Mass of 1 neutron})=4\times 1.0087=4.0348\text{ atomic mass units}$$
   • Total mass of the nucleons: $$\text{Total mass of nucleons}=3.0219+4.0348=7.0567\text{ atomic mass units}$$

3. Calculate the mass defect:

   • The mass defect is the difference between the total mass of the nucleons and the actual atomic mass: $$\text{Mass defect}=\text{Total mass of nucleons}-\text{Atomic mass of lithium}$$ $$\text{Mass defect}=7.0567-7.0144=0.0423\text{ atomic mass units}$$

Based on this calculation, the mass defect of lithium is:

B. 0.0423 atomic mass units