This section contains Assertion and Reason type questions each question has 4 choices (1)(2)(3)(4) out of which only one is correcT
Assertion(A):the horizontak rows in the periodic table are called periods or Mendeleev series
Reason(R):Elements having similar outer electronic configuration in their atoms are arranged in groups/families

Options

A. Both Assertion and Reason are correct and Reason ias the correct explanation of Assertion
B. Both Assertion and Reason are corect but Reason is not the correct explanation of Assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrcet

Answer

To solve the assertion and reason question, we will analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "the horizontal rows in the periodic table are called periods or Mendeleev series."
- This statement is **true**. In the periodic table, the horizontal rows are indeed referred to as periods, and Mendeleev was one of the early scientists to organize elements in this manner.

2. **Understanding the Reason (R)**:
- The reason states that "elements having similar outer electronic configuration in their atoms are arranged in groups/families."
- This statement is also **true**. Elements that have similar outer electron configurations are grouped together in the same vertical columns, known as groups or families.

3. **Evaluating the Relationship between Assertion and Reason**:
- While both the assertion and the reason are true, we need to determine if the reason correctly explains the assertion.
- The assertion discusses the horizontal arrangement (periods), while the reason talks about the vertical arrangement (groups/families).
- Therefore, the reason does not correctly explain the assertion.

4. **Conclusion**:
- The correct answer is that both statements are true, but the reason is not the correct explanation of the assertion.

### Final Answer:
- The correct option is (3): Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.