Which of the following minerals corners shared per silicate unit ?

Options

A. `CaMg[(SiO_(3))_(2)]`
B. `BaTi[Si_(3)O_(9)]`
C. `Ca_(2)Mg_(5)(Si_(4)O_(11))_(2)(OH)_(2)`
D. `Al(OH)_(4)[Si_(2)O_(5)]`

Answer

To solve the question "Which of the following minerals corners shared per silicate unit?", we need to analyze each mineral option provided and determine how many oxygen atoms are shared per silicate unit. Here’s a step-by-step solution:

### Step 1: Analyze the First Mineral
- **Mineral Formula**: CaMgSiO3 whole twice
- **Type of Silicate**: This mineral is classified as a chain silicate.
- **Empirical Formula**: The empirical formula can be represented as SiO3 (n = 2).
- **Oxygen Sharing**: In chain silicates, **2 oxygen atoms** are shared per silicate unit.

**Conclusion for Step 1**: This mineral does not meet the criteria since it shares 2 oxygen atoms.

### Step 2: Analyze the Second Mineral
- **Mineral Formula**: BaTiSi3O9
- **Type of Silicate**: This mineral is classified as a cyclic silicate.
- **Empirical Formula**: Similar to chain silicates, it can be represented as SiO3 (n = 2).
- **Oxygen Sharing**: In cyclic silicates, **2 oxygen atoms** are shared per silicate unit.

**Conclusion for Step 2**: This mineral also does not meet the criteria since it shares 2 oxygen atoms.

### Step 3: Analyze the Third Mineral
- **Mineral Formula**: Ca2Mg5Si4O11 whole twice OH whole twice
- **Type of Silicate**: This mineral is classified as a meta-tetra silicate.
- **Empirical Formula**: The empirical formula can be represented as Si4O11 (n = 6).
- **Oxygen Sharing**: In meta-tetra silicates, **2 oxygen atoms** are shared in half of the silicate unit, while **3 oxygen atoms** are not shared.

**Conclusion for Step 3**: This mineral does not meet the criteria since it shares 2 oxygen atoms in half of the unit.

### Step 4: Analyze the Fourth Mineral
- **Mineral Formula**: Al(OH)4Si2O5
- **Type of Silicate**: This mineral is classified as a 2-dimensional sheet silicate.
- **Empirical Formula**: The empirical formula can be represented as Si2O5 (n = 2).
- **Oxygen Sharing**: In 2D sheet silicates, **3 oxygen atoms** are shared per silicate unit.

**Conclusion for Step 4**: This mineral meets the criteria since it shares 3 oxygen atoms.

### Final Answer
Based on the analysis, the mineral that shares corners per silicate unit is:
- **Option D**: Al(OH)4Si2O5

### Summary
The correct answer is **Option D**, which shares **3 oxygen atoms** per silicate unit.

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