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Assertion (A)Cr and Cu are extra stable ...

Assertion (A)Cr and Cu are extra stable in the 3d-series.
Reason ( R) Half and completely filled set of orbitals are relatively more stable.

A

Both Assertion and Reason are correct and reason is explanation of the Assertion

B

Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion

C

Assertion is correct but Reason is incorrect

D

Both Assertion and Reason are incorrect

Text Solution

AI Generated Solution

The correct Answer is:
To solve the assertion and reason question regarding the stability of chromium (Cr) and copper (Cu) in the 3d series, we can follow these steps: ### Step 1: Understand the Assertion The assertion states that chromium and copper are extra stable in the 3d series. To analyze this, we need to look at the electronic configurations of these elements. ### Step 2: Determine the Electronic Configurations - **Chromium (Cr)**: The expected electronic configuration is \( \text{[Ar]} 3d^4 4s^2 \). However, the actual configuration is \( \text{[Ar]} 3d^5 4s^1 \). - **Copper (Cu)**: The expected electronic configuration is \( \text{[Ar]} 3d^9 4s^2 \). The actual configuration is \( \text{[Ar]} 3d^{10} 4s^1 \). ### Step 3: Analyze the Stability The deviations in the electronic configurations of chromium and copper indicate that they are more stable than expected. This is because: - A half-filled \( (3d^5) \) subshell in chromium provides extra stability. - A fully filled \( (3d^{10}) \) subshell in copper also provides extra stability. ### Step 4: Understand the Reason The reason states that half-filled and completely filled sets of orbitals are relatively more stable. This is a well-known principle in chemistry, as half-filled and fully filled orbitals have lower energy and are more stable due to symmetry and exchange energy. ### Step 5: Conclusion Both the assertion and the reason are correct. The reason correctly explains why chromium and copper are extra stable in the 3d series due to their unique electronic configurations. ### Final Answer - **Assertion (A)**: True - **Reason (R)**: True - **Explanation**: The reason is the correct explanation for the assertion. ---
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