Atomic Mass Unit Definition – Rankers Physics

Atomic Structure: Practice Problem & Solution

Assertion (A): On the atomic scale, mass is measured in atomic mass units (u). Reason (R): \(1u\) is \(1/12^{\text{th}}\) mass of one atom of \(C^{12}\)  \(1u = 1.66 \times 10^{-27}\text{ kg}\).  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Atomic Structure. Understanding the underlying formula is key to arriving at the correct answer below:

Atomic mass unit (u) is a standard unit for expressing mass on an atomic scale. It is defined as exactly \(1/12^{\text{th}}\) the mass of an unbound neutral atom of carbon-12. This definition directly supports why (A) is true and explains the basis for its measurement.

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