When `O_2` is adsorbed on ametallic surface, electron transfer occurs from the metal to ` O_2` The TRUE statement (s) regarding this adsorption is (are)

Options

A. `O_(2)` is physisorbed
B. heat is released
C. occupancy of `pi_(2p*)` of `O_(2)` increased
D. bond length of `O_(2)` is increased .

Answer

To analyze the adsorption of \( O_2 \) on a metallic surface and determine the true statements regarding this process, we can follow these steps:

### Step 1: Understanding Physisorption vs. Chemisorption
When \( O_2 \) is adsorbed on a metallic surface, it is important to determine whether the adsorption is physisorption (physical adsorption) or chemisorption (chemical adsorption). In this case, the video states that \( O_2 \) is physisorbed, meaning it is held to the metal surface by weak van der Waals forces rather than forming strong chemical bonds.

**Hint:** Consider the nature of the forces involved in adsorption to differentiate between physisorption and chemisorption.

### Step 2: Entropy Change During Adsorption
When \( O_2 \) is adsorbed onto the metallic surface, the degrees of freedom of the \( O_2 \) molecules decrease because they are now restricted in movement. This results in a decrease in entropy. Since the process of adsorption is associated with a decrease in entropy, energy is released during this process.

**Hint:** Think about how the movement of gas molecules is affected when they are adsorbed onto a surface.

### Step 3: Electron Transfer and Molecular Orbitals
The video mentions that there is an electron transfer from the metal to the \( O_2 \) molecule. This transfer increases the occupancy of the anti-bonding \( \pi^* \) orbitals of \( O_2 \). The electronic configuration of \( O_2 \) shows that the \( \pi^* \) orbitals are partially filled, and the addition of electrons will increase their occupancy.

**Hint:** Review the molecular orbital theory to understand how electron transfer affects the occupancy of molecular orbitals.

### Step 4: Bond Length and Bond Order
As electrons are added to the anti-bonding orbitals, the bond order of \( O_2 \) decreases. Since bond order is inversely related to bond length, a decrease in bond order implies an increase in bond length. Therefore, the bond length of \( O_2 \) increases as a result of the electron transfer.

**Hint:** Recall the relationship between bond order and bond length to understand how electron transfer impacts the stability of the bond.

### Conclusion
Based on the analysis:
- Statement A: \( O_2 \) is physisorbed - **True**
- Statement B: Heat is released during adsorption - **True**
- Statement C: Occupancy of \( \pi^* \) 2p orbital of \( O_2 \) is increased - **True**
- Statement D: Bond length of \( O_2 \) is increased - **True**

Thus, all statements A, B, C, and D are correct regarding the adsorption of \( O_2 \) on a metallic surface.

**Final Answer:** All statements A, B, C, and D are true.