The knowledge of valencies of various radicals helps us to write the formulae of chemical compounds. The total positive charge on positive ions ( cations ) is equal to the total negative charge on negative ions ( anions) in a molecule. Therefore, in writing the formula of a compound, the positive and negative ions are adjusted in such a way that the total number of positive charges of positive ions ( cations ) becomes equal to the total number of negative charges of negative ions ( anions) . There is another simple method for writing the formulae of ionic compounds. In this method, the valencies ( or positive or negative charges ) of the ions can be 'crossed over' to give subscripts. The purpose of crossing over of charges is to find the number of ions required to equalise the number of positive and negative charges.
The formula of the sulphate of an element X is `X_(2) ( SO_(4))_(3)`. The formula of nitride of element X will be

Options

A. `X_(2)N`
B. `XN_(2)`
C. `XN`
D. `X_(2)N_(3)`

Explanation

To find the formula of the nitride of element X, we will follow these steps:

### Step 1: Understand the given information
We know that the formula of the sulfate of element X is \(X_2(SO_4)_3\). The sulfate ion \((SO_4)^{2-}\) has a charge of -2.

### Step 2: Determine the charge of element X
Since the overall compound is neutral, we need to balance the total positive and negative charges. The sulfate ion contributes a total charge of:
\[ 3 \times (-2) = -6 \]
Given that there are 2 atoms of X in the formula, the total positive charge contributed by X must be +6 to balance the -6 charge from the sulfate ions. Therefore, each X must have a charge of:
\[ \frac{+6}{2} = +3 \]
So, the charge of element X is +3.

### Step 3: Identify the charge of nitride ion
The nitride ion is represented as \(N^{3-}\), which has a charge of -3.

### Step 4: Use the crisscross method to write the formula
To write the formula for the nitride of element X, we will use the crisscross method, where we take the charge of one ion and use it as the subscript for the other ion. Thus:
- The charge of X is +3, which becomes the subscript for N.
- The charge of N is -3, which becomes the subscript for X.

This gives us:
\[ X_1N_3 \text{ or simply } XN_3 \]

### Final Answer
The formula of the nitride of element X is \(XN_3\).

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