Which of the following complexes will mostly likely abosorb visible light ?
(At nos. Sc=21,Ti=22,C=23,Zn=30)

Options

A. `[Zn(NH_(3))_(6)]^(2+)`
B. `[Sc(H_(2)O)_(3)(NH_(3))_(3)]^(3+)`
C. `[Ti(en)_(2)(NH_(3))_(2)]^(4+)`
D. `[Cr(NH_(3))_(6)]^(3+)`

Explanation

To determine which complex will most likely absorb visible light, we need to identify the complex that contains unpaired electrons, as these are responsible for light absorption. Let's analyze the given complexes step by step.

### Step 1: Identify the complexes and their oxidation states

1. **Zn(NH3)6^2+**
- Zinc (Zn) has an atomic number of 30, and its electron configuration is [Ar] 4s² 3d¹⁰.
- In the +2 oxidation state, Zn loses its 4s electrons:
- Zn²⁺: [Ar] 3d¹⁰ (all electrons are paired, hence diamagnetic).

2. **Cr(NH3)6^3+**
- Chromium (Cr) has an atomic number of 24, and its electron configuration is [Ar] 4s¹ 3d⁵.
- In the +3 oxidation state, Cr loses 3 electrons (1 from 4s and 2 from 3d):
- Cr³⁺: [Ar] 3d³ (there are unpaired electrons, hence paramagnetic).

3. **Sc(NH3)3(H2O)3^3+**
- Scandium (Sc) has an atomic number of 21, and its electron configuration is [Ar] 4s² 3d¹.
- In the +3 oxidation state, Sc loses 3 electrons (2 from 4s and 1 from 3d):
- Sc³⁺: [Ar] 3d⁰ (all electrons are paired, hence diamagnetic).

4. **Ti(en)2(NH3)2^4+**
- Titanium (Ti) has an atomic number of 22, and its electron configuration is [Ar] 4s² 3d².
- In the +4 oxidation state, Ti loses 4 electrons (2 from 4s and 2 from 3d):
- Ti⁴⁺: [Ar] 3d⁰ (all electrons are paired, hence diamagnetic).

### Step 2: Determine the magnetic properties

- **Zn(NH3)6^2+**: Diamagnetic (no unpaired electrons).
- **Cr(NH3)6^3+**: Paramagnetic (3 unpaired electrons).
- **Sc(NH3)3(H2O)3^3+**: Diamagnetic (no unpaired electrons).
- **Ti(en)2(NH3)2^4+**: Diamagnetic (no unpaired electrons).

### Step 3: Conclusion

The only complex that contains unpaired electrons is **Cr(NH3)6^3+**, which is paramagnetic and therefore is most likely to absorb visible light.

### Final Answer
**Cr(NH3)6^3+** is the complex that will most likely absorb visible light.

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