Number of delocalized `e^(-)` pairs in squaric acid and dianion of squaric acid are respectively.

Options

A. `5&5`
B. `5&7`
C. `3&5`
D. `7&7`

Answer

To determine the number of delocalized electron pairs in squaric acid and its dianion, we will analyze the structures and resonance forms of both species.

### Step 1: Draw the structure of squaric acid
Squaric acid has a four-membered ring structure with two hydroxyl groups (-OH) and two carbonyl groups (C=O). The structure can be represented as follows:

```
O
//
HO-C C=O
\ /
C-C
// \
O O
```

### Step 2: Identify delocalized electrons in squaric acid
In squaric acid, we can identify the delocalized electrons through resonance. The oxygen atoms can donate their lone pairs, and the pi bonds can shift. The resonance structures will show how the electrons are delocalized.

1. **First resonance structure**:
- The lone pair from one of the hydroxyl groups can form a double bond with the adjacent carbon, while the double bond between the carbon and oxygen shifts to the oxygen atom.

2. **Second resonance structure**:
- The double bond between the carbon and oxygen can shift to the other carbon atom, and the lone pair from the other hydroxyl group can also participate in delocalization.

After analyzing the resonance structures, we find that there are **5 delocalized electron pairs** in squaric acid.

### Step 3: Draw the structure of the dianion of squaric acid
The dianion of squaric acid is formed when both hydroxyl groups lose their protons (H+), resulting in two negatively charged oxygen atoms. The structure can be represented as follows:

```
O^-
//
O^-C C=O
\ /
C-C
// \
O O
```

### Step 4: Identify delocalized electrons in the dianion of squaric acid
Similar to squaric acid, we can analyze the resonance structures of the dianion. The negatively charged oxygen atoms can also participate in resonance.

1. **First resonance structure**:
- The negative charge on one oxygen can be delocalized to form a double bond with the adjacent carbon, while the double bond between the carbon and oxygen shifts to the other oxygen atom.

2. **Second resonance structure**:
- The negative charge can shift between the two oxygen atoms, leading to different resonance forms.

After analyzing the resonance structures, we find that there are also **5 delocalized electron pairs** in the dianion of squaric acid.

### Final Answer
The number of delocalized electron pairs in squaric acid and its dianion are respectively **5 and 5**.