Which of the following species has tetrahedral geometry?

Options

A. `BH_(4)^(-)`
B. `NH_(2)^(-)`
C. `CO_(3)^(2-)`
D. `H_(3)O^(+)`

Explanation

To determine which of the given species has tetrahedral geometry, we will analyze each species based on their hybridization and steric number. The species we need to evaluate are BH4-, NH2-, carbonate (CO3^2-), and H3O+.

### Step 1: Calculate the Steric Number for Each Species

The formula to calculate the steric number (or hybridization) is:
\[ \text{Steric Number} = \frac{1}{2} \left( V + M - C + A \right) \]
Where:
- \( V \) = number of valence electrons of the central atom
- \( M \) = number of monovalent bonds formed
- \( C \) = charge of the cation (subtract this value)
- \( A \) = charge of the anion (add this value)

#### a) For BH4-
- Boron (B) has 3 valence electrons.
- It forms 4 monovalent bonds with hydrogen.
- There is a charge of -1 (anion).

Calculating:
\[ \text{Steric Number} = \frac{1}{2} \left( 3 + 4 + 1 \right) = \frac{8}{2} = 4 \]
- **Hybridization**: sp³
- **Geometry**: Tetrahedral

#### b) For NH2-
- Nitrogen (N) has 5 valence electrons.
- It forms 2 monovalent bonds with hydrogen.
- There is a charge of -1 (anion).

Calculating:
\[ \text{Steric Number} = \frac{1}{2} \left( 5 + 2 + 1 \right) = \frac{8}{2} = 4 \]
- **Hybridization**: sp³
- **Geometry**: Bent (due to lone pairs)

#### c) For Carbonate (CO3^2-)
- Carbon (C) has 4 valence electrons.
- It forms 3 bonds with oxygen.
- There is a charge of -2 (anion).

Calculating:
\[ \text{Steric Number} = \frac{1}{2} \left( 4 + 3 + 2 \right) = \frac{9}{2} = 4.5 \]
- **Hybridization**: sp² (not tetrahedral)
- **Geometry**: Trigonal planar

#### d) For H3O+
- Oxygen (O) has 6 valence electrons.
- It forms 3 bonds with hydrogen.
- There is a charge of +1 (cation).

Calculating:
\[ \text{Steric Number} = \frac{1}{2} \left( 6 + 3 - 1 \right) = \frac{8}{2} = 4 \]
- **Hybridization**: sp³
- **Geometry**: Pyramidal (due to lone pair)

### Step 2: Conclusion
From our analysis:
- **BH4-** has tetrahedral geometry.
- **NH2-** has a bent shape but is sp³ hybridized.
- **Carbonate (CO3^2-)** is trigonal planar and does not have tetrahedral geometry.
- **H3O+** has tetrahedral geometry but is pyramidal in shape.

### Final Answer
The species that has tetrahedral geometry is **BH4-** and **H3O+** (though H3O+ has a pyramidal shape).