Exams › JEE Advanced › Chemistry

Which of the following statements about tetrahedral voids in an FCC lattice of identical spheres is/are true?

1. Tetrahedral voids are formed by one corner sphere and three face-centred spheres in a unit cell.
2. Two tetrahedral voids can exist on one body diagonal in an FCC unit cell.
3. Number of tetrahedral voids equals the number of spheres in the lattice.
4. Volume of a tetrahedral void is half the volume of an octahedral void.

Correct answer: Tetrahedral voids are formed by one corner sphere and three face-centred spheres in a unit cell.

Solution

In FCC, each tetrahedral void is located at a corner of the unit cell surrounded by three face-centred atoms — statement A is correct. Also, each body diagonal passes through two tetrahedral voids — statement B is also correct. C is wrong (T-voids = 2 x atoms). D is wrong (octahedral voids are larger than tetrahedral).

Related JEE Advanced Chemistry questions

• Identify the accurate statement regarding lattice energy:
• An element forms a crystal with a face-centered cubic unit cell and an edge length of 200 pm. Calculate the density of the element if 200 g of it contains 24 × 10²³ atoms.
• Copper exhibits a face-centered cubic (fcc) arrangement. If the atomic radius of copper is 128 pm, what is the length of the unit cell edge?
• Sodium chloride forms cubic crystals when crystallized from water, but octahedral crystals when crystallized from a urea solution. How does this observation relate to the law of constancy of interfacial angles?
• If the edge length of a unit cell is 200 pm (200 × 10⁻¹² m), the unit cell's volume is calculated as (200 × 10⁻¹² m)³ = 8 × 10⁻³⁰ m³. For a face-centered cubic (fcc) structure, the number of atoms per unit cell (n) is 4. The mass of the unit cell is determined as n × A = 4 × 200 / 24 × 10²³ = 33.3 × 10⁻²³ g. Using the formula density = mass of unit cell / volume of unit cell, what is the density of the unit cell in g cm⁻³?
• In a face-centered cubic (fcc) lattice, the face diagonal equals four times the atomic radius. If the face diagonal of a copper crystal is given as 512 pm, what is the atomic radius?

⚔️ Practice JEE Advanced Chemistry free + battle 1v1 →