To determine which species has a plane triangular shape, we will analyze the given species one by one, focusing on their hybridization and molecular geometry.
### Step-by-Step Solution:
1. **Identify the Species**: The species we need to analyze are N3-, NO3-, NO2-, and CO2.
2. **Analyze N3- (Azide Ion)**:
- **Valence Electrons**: Each nitrogen has 5 valence electrons. For three nitrogen atoms, we have \(3 \times 5 = 15\) electrons. The negative charge adds one more electron, giving us a total of 16 valence electrons.
- **Structure**: The structure can be represented as \(N \equiv N - N^{-}\). The central nitrogen forms a triple bond with one nitrogen and a single bond with the other nitrogen.
- **Hybridization**: The central nitrogen has 2 bond pairs and 0 lone pairs, leading to \(sp\) hybridization. The shape is linear, not planar triangular.
3. **Analyze NO3- (Nitrate Ion)**:
- **Valence Electrons**: Nitrogen has 5 valence electrons, and each oxygen has 6. For three oxygens, we have \(3 \times 6 = 18\) electrons. The negative charge adds one more electron, giving us a total of \(5 + 18 + 1 = 24\) valence electrons.
- **Structure**: The structure is \(N\) with three single bonds to three oxygen atoms (one of which is a coordinate bond).
- **Hybridization**: The nitrogen has 3 bond pairs and 0 lone pairs, leading to \(sp^2\) hybridization. The shape is trigonal planar.
4. **Analyze NO2- (Nitrite Ion)**:
- **Valence Electrons**: Nitrogen has 5 valence electrons, and each oxygen has 6. For two oxygens, we have \(2 \times 6 = 12\) electrons. The negative charge adds one more electron, giving us a total of \(5 + 12 + 1 = 18\) valence electrons.
- **Structure**: The structure is \(N\) with one double bond to one oxygen and one single bond to the other oxygen. The second oxygen has a lone pair.
- **Hybridization**: The nitrogen has 2 bond pairs and 1 lone pair, leading to \(sp^2\) hybridization. The shape is bent, not planar triangular.
5. **Analyze CO2 (Carbon Dioxide)**:
- **Valence Electrons**: Carbon has 4 valence electrons, and each oxygen has 6. For two oxygens, we have \(2 \times 6 = 12\) electrons. This gives a total of \(4 + 12 = 16\) valence electrons.
- **Structure**: The structure is \(O = C = O\) with two double bonds.
- **Hybridization**: The carbon has 2 bond pairs and 0 lone pairs, leading to \(sp\) hybridization. The shape is linear, not planar triangular.
### Conclusion:
The only species with a planar triangular shape is **NO3- (Nitrate Ion)**.
### Final Answer:
**NO3- (Nitrate Ion)** has a planar triangular shape.
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