What is the bond order between C and C in `H - C -= C-H` ?

Answer

To determine the bond order between the carbon atoms in the molecule `H - C ≡ C - H` (ethyne), we can follow these steps:

### Step 1: Understand Bond Order
Bond order is defined as the number of shared electron pairs between two atoms. It can be calculated using the formula:

\[ \text{Bond Order} = \frac{\text{Number of bonding electrons} - \text{Number of antibonding electrons}}{2} \]

However, for simpler cases, we can also determine bond order based on the type of bonds present between the atoms.

### Step 2: Identify the Type of Bonds
In the molecule `H - C ≡ C - H`, we need to focus on the bonds between the carbon atoms. The structure shows that there is a triple bond between the two carbon atoms.

### Step 3: Count the Bonds
A triple bond consists of three shared electron pairs:
- One sigma (σ) bond
- Two pi (π) bonds

Thus, between the two carbon atoms, there are three bonds in total.

### Step 4: Determine the Bond Order
Since there are three shared electron pairs (or bonds) between the carbon atoms, the bond order can be directly concluded as:

\[ \text{Bond Order} = 3 \]

### Final Answer
The bond order between carbon and carbon in `H - C ≡ C - H` is **3**.

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