The formula of a compound when a positive radical with valency 2 and negative radical with valency 1 combine is _______ .

Options

A. `B_(2)A`
B. `A_(2)B`
C. `AB_(2)`
D. AB

Answer

To find the formula of a compound formed by a positive radical with a valency of 2 and a negative radical with a valency of 1, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Radicals and Their Valencies**:
- Let the positive radical be represented as \( A \) with a valency of \( +2 \).
- Let the negative radical be represented as \( B \) with a valency of \( -1 \).

2. **Write the Charges**:
- The positive radical \( A \) has a charge of \( +2 \) (i.e., \( A^{+2} \)).
- The negative radical \( B \) has a charge of \( -1 \) (i.e., \( B^{-1} \)).

3. **Determine the Ratio of Radicals**:
- To form a neutral compound, the total positive charge must balance the total negative charge.
- Since \( A \) has a valency of 2, it can combine with two \( B \) radicals (since each \( B \) has a valency of 1).

4. **Cross-Multiply the Valencies**:
- The valency of \( A \) is 2, and the valency of \( B \) is 1.
- To find the formula, we can cross-multiply:
- For \( A \): 1 (from \( B \))
- For \( B \): 2 (from \( A \))
- This gives us the formula \( AB_2 \).

5. **Write the Final Formula**:
- Therefore, the formula of the compound formed by the combination of the positive radical \( A \) and the negative radical \( B \) is \( AB_2 \).

### Final Answer:
The formula of the compound when a positive radical with valency 2 and a negative radical with valency 1 combine is **AB₂**.