Question

The nucleus of oxygen atom contains 8 protons and 8 neutrons. What is the mass defect in amu? [Given Mass of proton = 1.00727 amu Mass of neutron = 1.00866 amu and the mass of oxygen nucleus = 15.99053 amu.]

• A. 0.12691 amu
• B. 0.13692 amu
• C. 0.13691 amu
• D. 0.12961 amu

Hint:

Mass defect = (sum of nucleon masses) – (actual nuclear mass).

Answer 1

The Correct Option is C

Step 1: Write mass of nucleons.
Total mass of protons:
\[ 8 \times 1.00727 = 8.05816 \]

Step 2: Write mass of neutrons.
\[ 8 \times 1.00866 = 8.06928 \]

Step 3: Total mass before formation.
\[ = 8.05816 + 8.06928 \]
\[ = 16.12744 \]

Step 4: Write actual nuclear mass.
\[ = 15.99053 \]

Step 5: Calculate mass defect.
\[ \Delta m = 16.12744 - 15.99053 \]

Step 6: Final calculation.
\[ \Delta m = 0.13691 \, \text{amu} \]

Step 7: Final Answer.
\[ \boxed{0.13691 \, \text{amu}} \]