What is the bond order of `H_(2)^(-)` ion ?

Answer

To find the bond order of the H₂⁻ ion, we can follow these steps:

### Step 1: Understand the Molecular Orbitals
The H₂⁻ ion consists of two hydrogen atoms, each contributing one electron. However, since it is an anion (H₂⁻), there is one additional electron, making a total of three electrons.

### Step 2: Draw the Molecular Orbital Diagram
For two hydrogen atoms, the molecular orbitals formed are:
- One bonding molecular orbital (σ 1s)
- One antibonding molecular orbital (σ* 1s)

### Step 3: Fill the Molecular Orbitals
We have three electrons to place in the molecular orbitals:
- The first two electrons will fill the bonding orbital (σ 1s): σ 1s²
- The third electron will occupy the antibonding orbital (σ* 1s): σ* 1s¹

### Step 4: Write the Electronic Configuration
The electronic configuration for H₂⁻ can be represented as:
- σ 1s² (bonding)
- σ* 1s¹ (antibonding)

### Step 5: Calculate the Bond Order
The formula for bond order (B.O.) is given by:
\[ \text{Bond Order} = \frac{1}{2} (\text{Number of bonding electrons} - \text{Number of antibonding electrons}) \]

In our case:
- Number of bonding electrons = 2 (from σ 1s²)
- Number of antibonding electrons = 1 (from σ* 1s¹)

Now substituting these values into the formula:
\[ \text{Bond Order} = \frac{1}{2} (2 - 1) = \frac{1}{2} \]

### Conclusion
The bond order of the H₂⁻ ion is 0.5.

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