If the formulae of respective chlorides of X and Y are `XCl_(3) "and" YCl_(4)`, respectively, then the valencies of X and Y are

Options

A. 3 and 2
B. 3 and 4
C. 1 and 1
D. 1 and 4

Answer

To determine the valencies of elements X and Y from their respective chlorides \(XCl_3\) and \(YCl_4\), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Valency**:
Valency is the measure of an element's ability to combine with other elements, which is often represented by the charge on the element when it forms a compound.

2. **Analyzing the Chloride Compounds**:
- The formula for the chloride of X is \(XCl_3\).
- The formula for the chloride of Y is \(YCl_4\).

3. **Determining the Charge of Chloride Ion**:
- The chloride ion (\(Cl\)) has a charge of \(-1\).

4. **Calculating the Total Negative Charge from Chloride Ions**:
- For \(XCl_3\): There are 3 chloride ions, so the total negative charge is:
\[ 3 \times (-1) = -3 \]
- For \(YCl_4\): There are 4 chloride ions, so the total negative charge is:
\[ 4 \times (-1) = -4 \]

5. **Finding the Charge on X**:
- Since \(XCl_3\) is a neutral compound, the positive charge from X must balance the total negative charge from the chloride ions:
\[ \text{Charge on } X + (-3) = 0 \implies \text{Charge on } X = +3 \]
- Therefore, the valency of X is **3**.

6. **Finding the Charge on Y**:
- Similarly, for \(YCl_4\), the positive charge from Y must balance the total negative charge from the chloride ions:
\[ \text{Charge on } Y + (-4) = 0 \implies \text{Charge on } Y = +4 \]
- Therefore, the valency of Y is **4**.

### Conclusion:
- The valency of X is **3**.
- The valency of Y is **4**.