Co-ordinate bond is absent in

Options

A. `BH_4^(Theta)`
B. `CO_3^(-2)`
C. `H_3O^(+)`
D. `NH_4^(o+)`

Explanation

To determine where a coordinate bond is absent, we need to analyze the bonding in different chemical species. Let's break down the question step by step.

### Step 1: Understanding Coordinate Bonds
A coordinate bond (or dative bond) is formed when one atom donates a pair of electrons to another atom that does not have a complete octet. This bond is represented by an arrow pointing from the donor atom to the acceptor atom.

**Hint:** Remember that a coordinate bond involves the donation of a lone pair from one atom to another.

### Step 2: Analyzing the Given Compounds
We need to evaluate the compounds mentioned in the video transcript: BH4^-, CO3^2-, H3O^+, and NH4^+.

1. **BH4^- (Boron Tetrahydride Ion)**:
- Boron has 3 valence electrons and can form 4 bonds by accepting an electron pair from a hydrogen atom, resulting in one coordinate bond.
- **Conclusion:** BH4^- has a coordinate bond.

2. **CO3^2- (Carbonate Ion)**:
- In CO3^2-, carbon is bonded to three oxygen atoms through covalent bonds. There are no lone pairs being donated to form a bond.
- **Conclusion:** CO3^2- does not have a coordinate bond.

3. **H3O^+ (Hydronium Ion)**:
- In H3O^+, oxygen donates a lone pair to bond with an additional hydrogen ion (H^+), forming a coordinate bond.
- **Conclusion:** H3O^+ has a coordinate bond.

4. **NH4^+ (Ammonium Ion)**:
- In NH4^+, nitrogen donates a lone pair to bond with an additional hydrogen ion (H^+), forming a coordinate bond.
- **Conclusion:** NH4^+ has a coordinate bond.

### Step 3: Conclusion
From the analysis, we can conclude that the coordinate bond is absent in **CO3^2-**.

**Final Answer:** The coordinate bond is absent in CO3^2-.

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