NEET Biology Complete Course by Moniba Madam - Watch Full Playlist

Test Index

Class 12 NEET Physics Atoms and Nuclei Part 1

© examsnet.com

Question : 40 of 103

Marks: +1, -0

M_{n}

M_{p}

represent the mass of neutron and proton respectively. An element having mass

M

N

Z

protons, then the correct relation will be

$M < \left( N \cdot M_{n}+Z \cdot M_{p} \right)$
$M > \left( N \cdot M_{n}+Z \cdot M_{p} \right)$
$M = \left( N \cdot M_{n}+Z \cdot M_{p} \right)$
$M = N \left( M_{n}+M_{p} \right)$

Solution:

Concept:

The actual mass of a nucleus is less than the sum of masses of its constituent nucleons due to mass defect and binding energy.

Explanation:

1. Composition of nucleus: An element with mass

M

contains

N

neutrons and

Z

protons.

2. Sum of individual masses: If we add up the masses of all nucleons separately:

Total mass of neutrons = $N \cdot M_n$
Total mass of protons = $Z \cdot M_p$
Sum = $N \cdot M_n + Z \cdot M_p$

3. Mass defect: When nucleons combine to form a nucleus, some mass is converted into binding energy (Einstein's

E = mc^2

). This "missing mass" is called mass defect.

4. Actual nucleus mass: Due to this mass defect:

M < (N \cdot M_n + Z \cdot M_p)

5. Why? The binding energy that holds the nucleus together comes from the conversion of mass. Therefore, the actual nuclear mass is always less than the sum of individual nucleon masses.

Answer:

Option A:

M < (N \cdot M_n + Z \cdot M_p)

This is the correct relation. The actual mass of the nucleus is always less than the sum of the masses of its constituent nucleons due to mass defect.

© examsnet.com

Go to Question:

Prev Question

Next Question