Question

What is meant by mass number of a nucleus? How is it different from atomic number?

Hint:

Mass number is the sum of protons and neutrons, while atomic number is only the number of protons in the nucleus.

Answer 1

Step 1: Definition of Mass Number.
The mass number \( A \) of a nucleus is the total number of protons and neutrons in the nucleus. It is given by the formula: \[ A = Z + N \] Where:
- \( Z \) is the atomic number (number of protons),
- \( N \) is the number of neutrons.
Step 2: Definition of Atomic Number.
The atomic number \( Z \) of an element is the number of protons in the nucleus of the atom, which determines the element’s identity.
Step 3: Difference Between Mass Number and Atomic Number.
The atomic number represents the number of protons in an atom, while the mass number is the sum of the number of protons and neutrons in the nucleus.
Final Answer:
- The mass number \( A \) is the sum of protons and neutrons.
- The atomic number \( Z \) is the number of protons in the nucleus.