Assertion (A): Copper exhibits variable valency.
Reason (R): Copper loses two electrons from its valence shell and it can also lose one more electron from the second last shell.

Options

A. Both A and R are true and R is the correct explanation for A.
B. Both A and R are true but R is not the correct explanation for A.
C. A is true and R is false.
D. S false and R is true.

Explanation

To analyze the assertion and reason provided in the question, let's break it down step by step.

### Step 1: Understanding the Assertion
- **Assertion (A)**: Copper exhibits variable valency.
- **Explanation**: Variable valency means that an element can lose different numbers of electrons to form ions with different charges. Copper is known to exhibit variable valency, specifically +1 and +2.

### Step 2: Understanding the Reason
- **Reason (R)**: Copper loses two electrons from its valence shell and can also lose one more electron from the second last shell.
- **Explanation**: The electronic configuration of copper (Cu) is [Ar] 3d10 4s1. This means that copper has one electron in the 4s orbital (which is its valence shell) and ten electrons in the 3d orbital (which is the second last shell).

### Step 3: Analyzing the Reason
- When copper loses electrons to form ions, it can lose:
- The single electron in the 4s orbital to form Cu⁺ (valency +1).
- It can also lose one of the electrons from the 3d orbital to form Cu²⁺ (valency +2).
- However, the statement that copper loses "two electrons from its valence shell" is misleading. The valence shell refers specifically to the outermost shell, which in copper's case is the 4s shell, where only one electron is present.

### Step 4: Conclusion
- **Assertion (A)** is true because copper does exhibit variable valency.
- **Reason (R)** is false because it incorrectly states that copper loses two electrons from its valence shell when it actually loses one from the 4s shell and can lose one from the 3d shell.

### Final Answer
- The assertion is true, and the reason is false.