Question

Identify the compound formed from elements X, Y, Z having oxidation states $+2$, $+5$, $-2$ respectively.

• A. $\text{X}(\text{Y}_4\text{Z})$
• B. $\text{X}_3(\text{YZ}_4)_2$
• C. $\text{X}_3(\text{YZ}_2)_2$
• D. $\text{XYZ}_2$

Hint:

Think of this as a classic criss-cross valency problem! Treat the polyatomic cluster $(\text{YZ}_4)$ as a single radical unit. Its net charge is $+5 + 4(-2) = -3$. Criss-crossing the valencies of $\text{X}^{2+}$ and $(\text{YZ}_4)^{3-}$ immediately delivers the formula $\text{X}_3(\text{YZ}_4)_2$!

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We are given three elements X, Y, and Z with oxidation states $+2$, $+5$, and $-2$ respectively. We need to determine which chemical formula represents a stable, electrically neutral compound.

Step 2: Key Formula or Approach:
For any neutral chemical formula unit, the sum of the oxidation states of all constituent atoms must equal exactly zero:
$$\sum (\text{Number of atoms} \times \text{Oxidation state}) = 0$$

Step 3: Detailed Explanation:
Let's test each option by calculating the total net charge:
(A) $\text{X}(\text{Y}_4\text{Z})$:
$$\text{Total charge} = (+2) + 4(+5) + 1(-2) = 2 + 20 - 2 = +20 \neq 0$$ (B) $\text{X}_3(\text{YZ}_4)_2$:
First, determine the net charge of the polyatomic group $(\text{YZ}_4)$:
$$\text{Group charge} = (+5) + 4(-2) = 5 - 8 = -3$$ Now, combine 3 units of X and 2 units of the $(\text{YZ}_4)$ group:
$$\text{Total charge} = 3(+2) + 2(-3) = 6 - 6 = 0$$ Since the sum is perfectly zero, this represents a stable, neutral chemical compound.
(C) $\text{X}_3(\text{YZ}_2)_2$:
Group charge of $(\text{YZ}_2) = (+5) + 2(-2) = +1$
$$\text{Total charge} = 3(+2) + 2(+1) = 6 + 2 = +8 \neq 0$$ (D) $\text{XYZ}_2$:
$$\text{Total charge} = (+2) + (+5) + 2(-2) = 7 - 4 = +3 \neq 0$$ Therefore, option (B) is the only valid neutral structure.

Step 4: Final Answer:
The compound formed is $\text{X}_3(\text{YZ}_4)_2$, which corresponds to option (B).