Which of the following is correct ?

Options

A. According to `VSEPR` theory `SNCI_(2)` in a linear molecule
B. The number of electrons present in the valence shell in `SF_(6)` is 12
C. The rates of ionic reactions are very slow
D. The correct order of ability form ionic compounds among `Na^(o+),Mg^(2+),` and `A1^(+3)` is `A1^(+3) gt Mg^(+2) gt Na^(o+)` .

Explanation

To solve the question "Which of the following is correct?" we need to analyze each statement provided. Let's break it down step by step.

### Step 1: Analyze the first statement about SnCl2
- **Statement**: According to VSEPR theory, SnCl2 is a linear molecule.
- **Calculation**:
- Count the valence electrons:
- Sn (Tin) has 4 valence electrons.
- Cl (Chlorine) has 7 valence electrons, and there are 2 Cl atoms: 2 × 7 = 14.
- Total = 4 (from Sn) + 14 (from Cl) = 18 valence electrons.
- Divide by 8 to find the bonding pairs and lone pairs:
- 18 ÷ 8 = 2 with a remainder of 2.
- This means there are 2 bond pairs and 1 lone pair.
- **Shape**: With 2 bond pairs and 1 lone pair, the shape is V-shaped (or bent), not linear.
- **Conclusion**: The first statement is **wrong**.

### Step 2: Analyze the second statement about SF6
- **Statement**: The number of electrons present in the valence shell of SF6 is 12.
- **Calculation**:
- Sulfur (S) has 6 valence electrons.
- In SF6, sulfur forms 6 bonds with fluorine, contributing 6 more electrons (2 electrons per bond).
- Total = 6 (from S) + 6 (from bonds) = 12 electrons.
- **Conclusion**: The second statement is **correct**.

### Step 3: Analyze the third statement about ionic reactions
- **Statement**: The rate of ionic reactions is very slow.
- **Conclusion**: This statement is **false**. Ionic reactions, such as precipitation reactions, often occur rapidly.

### Step 4: Analyze the fourth statement about ionic compounds
- **Statement**: The correct order of ability to form ionic compounds among sodium, magnesium, and aluminum ions.
- **Analysis**:
- The ability to form ionic compounds is related to ionization enthalpy.
- Sodium (Na) has the lowest ionization enthalpy, followed by magnesium (Mg), and aluminum (Al) has the highest.
- Therefore, the order of tendency to form ionic compounds is Na > Mg > Al.
- **Conclusion**: The fourth statement is **false**.

### Final Conclusion
After analyzing all statements:
- The only correct statement is the second one regarding SF6.

Thus, the correct answer is **B**.