A compound MpXq has cubic-close packing (c.c.p) arrangement of X. Its unit-cell structure is shown below. The empirical formula of the compound is:
A) MX

B) MX2

C) M2X

D) M5X14

To determine the empirical formula of the compound \( MpXq \) with a cubic-close packing (c.c.p.) arrangement of \( X \), we need to analyze the arrangement of the atoms in the unit cell and how many atoms of \( M \) and \( X \) are present.

### Step 1: Understanding the c.c.p. arrangement
In a cubic-close packing structure, also known as face-centered cubic (FCC), the packing is efficient, and the unit cell consists of:

- **Corner atoms**: There are 8 corners in the unit cell, and each corner atom contributes \(\frac{1}{8\) of an atom to the unit cell.
- **Face atoms**: There are 6 faces in the unit cell, and each face atom contributes \(\frac{1}{2}\) of an atom to the unit cell.

Calculating the total number of \( X \) atoms in the unit cell:

\[
\text{Total } X \text{ atoms} = 8 \times \frac{1}{8} + 6 \times \frac{1}{2} = 1 + 3 = 4
\]

Thus, there are **4 atoms of \( X \)** in the cubic-close packing unit cell.

### Step 2: Determining the number of \( M \) atoms
The general formula of the compound is given as \( MpXq \). For c.c.p. structures, it is common for the metal ions \( M \) to occupy the octahedral or tetrahedral voids in the structure.

#### Voids in the c.c.p. structure
In a cubic-close packing:
- **Octahedral voids**: There is 1 octahedral void per unit cell.
- **Tetrahedral voids**: There are 8 tetrahedral voids per unit cell.

If \( M \) occupies octahedral voids, there is 1 \( M \) atom per unit cell. If it occupies tetrahedral voids, there are 8 \( M \) atoms per unit cell.

### Step 3: Analyzing the possible formulas
The possible empirical formulas can be derived based on the number of \( M \) and \( X \) atoms:

1. If \( M \) occupies octahedral voids:
- Empirical formula = \( MX_4 \) (not listed in the options)

2. If \( M \) occupies tetrahedral voids:
- Empirical formula = \( M_8X_4 \) or simplified to \( M_2X \).

Since this matches the formula with \( M \) occupying tetrahedral voids, we can conclude:

### Step 4: Conclusion
The empirical formula of the compound \( MpXq \) is:

\[
\text{Answer: } \text{C) } M_2X
\]

This matches our findings based on the c.c.p. structure and the position of \( M \) within it.