Question

An atom of lithium contains 3 electrons, 3 protons and 4 neutrons. Its mass number is:

• A. 3
• B. 4
• C. 7
• D. 10

Hint:

The mass number is the total count of nucleons (protons and neutrons). The number of electrons determines the charge, not the mass number.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The mass number of an atom is defined as the total number of nucleons (protons + neutrons) in the nucleus.
Step 2: Key Formula or Approach:
\[ \text{Mass Number (A)} = \text{Number of Protons (Z)} + \text{Number of Neutrons (N)} \]
Step 3: Detailed Explanation:
Given:
Protons = 3
Neutrons = 4
Electrons = 3 (Electrons are not counted in the mass number because their mass is negligible).
\[ A = 3 + 4 = 7 \]
Step 4: Final Answer:
The mass number is 7.