Assertion : Isobars are identical in chemical properties.
Reason : Isobars have different mass number.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question regarding the assertion and reason about isobars, we will analyze each statement step by step.

### Step 1: Understand the Definition of Isobars
Isobars are defined as atoms that have the same mass number but different atomic numbers. The mass number is the total number of protons and neutrons in the nucleus, while the atomic number is the number of protons in the nucleus.

**Hint:** Remember that isobars have the same mass number but different atomic numbers.

### Step 2: Analyze the Assertion
The assertion states that "Isobars are identical in chemical properties." Since isobars have different atomic numbers, they will have different chemical properties. The atomic number is crucial because it determines the number of electrons and thus the chemical behavior of the element.

**Hint:** Chemical properties are primarily determined by the atomic number.

### Step 3: Analyze the Reason
The reason states that "Isobars have different mass numbers." This statement is incorrect because isobars, by definition, have the same mass number. Therefore, this reason does not support the assertion.

**Hint:** Check the definition of isobars to clarify their mass numbers.

### Step 4: Conclusion
Since both the assertion and the reason are false, we conclude that both statements do not hold true.

**Final Answer:** Both the assertion and the reason are false.