Among the following ions the p `pi`- d `pi` overlap could be present in

Options

A. `NO_2^-`
B. `NO_3^-`
C. `PO_4^(3-)`
D. `CO_3^(2-)`

Explanation

To determine which ions can exhibit pπ-dπ overlap, we need to analyze the electronic configuration and the presence of d orbitals in the given ions. Here’s a step-by-step solution:

### Step 1: Understand the Concept of pπ-dπ Overlap
pπ-dπ overlap occurs when there is a bonding interaction between p orbitals (typically from a non-metal) and d orbitals (typically from a transition metal). For this overlap to occur, one of the atoms must have accessible d orbitals, which are present in elements from the third period onwards.

**Hint:** Remember that p orbitals are found in groups 13-18, while d orbitals start appearing in the transition metals from the third period.

### Step 2: Identify the Period of the Elements
We need to identify the elements in the ions provided and determine their periods in the periodic table:
- **Nitrogen (N)** - Period 2
- **Oxygen (O)** - Period 2
- **Carbon (C)** - Period 2
- **Phosphorus (P)** - Period 3

**Hint:** Elements in the second period only have s and p orbitals, while elements in the third period can have s, p, and d orbitals.

### Step 3: Analyze the Given Ions
Now let's analyze the ions mentioned:
1. **NO2 (Nitrogen Dioxide)** - Contains N and O, both from the second period. No d orbitals are present.
2. **CO2 (Carbon Dioxide)** - Contains C and O, both from the second period. No d orbitals are present.
3. **PO4^3- (Phosphate Ion)** - Contains P from the third period and O from the second period. P has d orbitals available for overlap with the p orbitals of O.

**Hint:** Look for the presence of d orbitals in the elements of the ions to determine if pπ-dπ overlap is possible.

### Step 4: Conclusion
Among the ions given, only the phosphate ion (PO4^3-) can exhibit pπ-dπ overlap due to the presence of phosphorus, which has d orbitals, and oxygen, which has p orbitals.

**Final Answer:** The pπ-dπ overlap could be present in the ion **PO4^3-**.