Assertion (A): In triad, the three elements have same gaps of atomic masses. ,br> Reason (R): Elements in a triad have similar properties.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is true but R is false.
D. A is false and R is true.

Explanation

To solve the question regarding the assertion and reason about triads in chemistry, let's break it down step by step.

### Step 1: Understand the Assertion
The assertion states: "In triad, the three elements have the same gaps of atomic masses."
- In a triad, specifically referring to Dobereiner's triads, the three elements are arranged in such a way that the atomic mass of the middle element is approximately the average of the atomic masses of the other two elements. This means that the gaps between the atomic masses of the elements are not necessarily the same.

### Step 2: Analyze the Reason
The reason states: "Elements in a triad have similar properties."
- This is true. Dobereiner's triads were based on the observation that elements in a triad exhibit similar chemical properties. For example, if we consider the triad of lithium, sodium, and potassium, they all have similar reactivity and properties.

### Step 3: Conclusion
Now, we can conclude the truth values of both the assertion and the reason:
- The assertion (A) is **false** because the three elements do not have the same gaps in atomic masses.
- The reason (R) is **true** because elements in a triad do exhibit similar properties.

### Final Answer
Thus, the correct answer is: Assertion (A) is false, and Reason (R) is true.