Question

Assertion (A): Atomic mass of sodium is 23.

Reason (R): An atom of sodium is 23 times heavier than an atom of Carbon 12 isotope.

Options

• If both A and R are true, and R is the correct explanation of A.

• If both A and R are true, but R is not the correct explanation of A.

• If A is true, but R is false.

• If both A and R are false.

Answer 1

If A is true, but R is false.

Explanation:

The assertion is true because the relative atomic mass of sodium is factual at 23 u. The reason is false because an atom of sodium is actually 23 times heavier than one-twelfth of the mass of a carbon-12 atom, not the entire carbon-12 atom itself. If it were 23 times heavier than a full carbon-12 atom, its atomic mass would mistakenly be calculated as 23 × 12 = 276 u.