Predict the formula of the stable binary compounds that would be formed by the combination of the following pairs of elements.
a.Lithium and oxygen
b. Magnesium and nitrogen
c. Aluminium and iodine
d. Silicon and oxygen
e. Phosphorus and fluorine
f. Element `71` and fluorine

Options

A. `MgN_(2),SiO_(2)`
B. `Mg_(3)N_(2),SiO_(2)`
C. `Mg_(2)N_(3),Si_(2)O_(3)`
D. `MgN,SiO_(2)`

Answer

To predict the formulas of the stable binary compounds formed by the given pairs of elements, we will follow these steps:

### Step 1: Lithium and Oxygen
- **Valency of Lithium (Li)**: +1
- **Valency of Oxygen (O)**: -2
- **Using the crisscross method**:
- Lithium has a valency of 1, and oxygen has a valency of 2.
- We write Li and O with their respective valencies: Li^1 O^2.
- Crisscross the valencies: Li becomes subscript 2, and O becomes subscript 1.
- **Formula**: Li2O

### Step 2: Magnesium and Nitrogen
- **Valency of Magnesium (Mg)**: +2
- **Valency of Nitrogen (N)**: -3
- **Using the crisscross method**:
- Magnesium has a valency of 2, and nitrogen has a valency of 3.
- We write Mg and N with their respective valencies: Mg^2 N^3.
- Crisscross the valencies: Mg becomes subscript 3, and N becomes subscript 2.
- **Formula**: Mg3N2

### Step 3: Aluminium and Iodine
- **Valency of Aluminium (Al)**: +3
- **Valency of Iodine (I)**: -1
- **Using the crisscross method**:
- Aluminium has a valency of 3, and iodine has a valency of 1.
- We write Al and I with their respective valencies: Al^3 I^1.
- Crisscross the valencies: Al becomes subscript 1, and I becomes subscript 3.
- **Formula**: AlI3

### Step 4: Silicon and Oxygen
- **Valency of Silicon (Si)**: +4
- **Valency of Oxygen (O)**: -2
- **Using the crisscross method**:
- Silicon has a valency of 4, and oxygen has a valency of 2.
- We write Si and O with their respective valencies: Si^4 O^2.
- Crisscross the valencies: Si becomes subscript 2, and O becomes subscript 4.
- **Formula**: Si2O4, which simplifies to SiO2

### Step 5: Phosphorus and Fluorine
- **Valency of Phosphorus (P)**: +3
- **Valency of Fluorine (F)**: -1
- **Using the crisscross method**:
- Phosphorus has a valency of 3, and fluorine has a valency of 1.
- We write P and F with their respective valencies: P^3 F^1.
- Crisscross the valencies: P becomes subscript 1, and F becomes subscript 3.
- **Formula**: PF3

### Step 6: Element 71 and Fluorine
- **Element 71**: Lutetium (Lu)
- **Valency of Lutetium (Lu)**: +3
- **Valency of Fluorine (F)**: -1
- **Using the crisscross method**:
- Lutetium has a valency of 3, and fluorine has a valency of 1.
- We write Lu and F with their respective valencies: Lu^3 F^1.
- Crisscross the valencies: Lu becomes subscript 1, and F becomes subscript 3.
- **Formula**: LuF3

### Summary of Formulas
- a. Lithium and Oxygen: **Li2O**
- b. Magnesium and Nitrogen: **Mg3N2**
- c. Aluminium and Iodine: **AlI3**
- d. Silicon and Oxygen: **SiO2**
- e. Phosphorus and Fluorine: **PF3**
- f. Element 71 and Fluorine: **LuF3**