Advertisements
Advertisements
प्रश्न
How many atoms constitute one unit cell of a face-centered cubic crystal?
How many atoms are present per unit cell in a face-centred cubic system?
In a face-centred arrangement of atoms of an element, what will be the numbers of atoms present in respective unit cells? Justify your answer with calculation.
Advertisements
उत्तर
The cubic unit cell in face-centred cubic systems is made up of one atom at each of the cube’s eight corners and atoms at the centre of each of the cube’s six faces. Eight unit cells share each corner atom evenly, contributing 1/8 of the unit cell. Two unit cells share equally each atom located in the centre of the face, contributing half of the two unit cells.
∴ Number of atoms in a face-centred unit cell = `(8 xx 1/8) + (6 xx 1/2)`
= 1 + 3
= 4 atoms
Thus, the unit cell of a face-centred cubic system contains 4 atoms.
APPEARS IN
संबंधित प्रश्न
Gold occurs as face centred cube and has a density of 19.30 kg dm-3. Calculate atomic radius of gold. (Molar mass of Au = 197)
Face centred cubic crystal lattice of copper has density of 8.966 g.cm-3. Calculate the volume of the unit cell. Given molar mass of copper is 63.5 g mol-1 and Avogadro number NA is 6.022 x 1023 mol-1
An element crystallises in a b.c.c lattice with cell edge of 500 pm. The density of the element is 7.5g cm-3. How many atoms are present in 300 g of the element?
Distinguish between Hexagonal and monoclinic unit cells
Explain how much portion of an atom located at (i) corner and (ii) body-centre of a cubic unit cell is part of its neighbouring unit cell.
What is the coordination number of atoms in a cubic close-packed structure?
How can you determine the atomic mass of an unknown metal if you know its density and the dimension of its unit cell? Explain.
Explain with reason sign conventions of ΔS in the following reaction
N2(g) + 3H2(g) → 2NH3(g)
Explain with reason sign conventions of ΔS in the following reaction
CO2(g) → CO2(g)
The density of silver having an atomic mass of 107.8 g mol- 1 is 10.8 g cm-3. If the edge length of cubic unit cell is 4.05 × 10- 8
cm, find the number of silver atoms in the unit cell.
( NA = 6.022 × 1023, 1 Å = 10-8 cm)
The number of atoms per unit cell in a body centered cubic structure is ____________.
An atom located at the body center of a cubic unit cell is shared by ____________.
Volume of unit cell occupied in face-centered cubic arrangement is ____________.
An element forms a cubic unit cell with edge length 405 pm. Molar mass of this element is 2.7 × 10−2 kg/mol and its density is given as 2.7 × 103 kg/m3. How many atoms of these elements are present per unit cell?
A substance forms face-centered cubic crystals. Its density is 1.984 g/cm3 and the length of the edge of the unit cell is 630 pm. Calculate the molar mass in g/mol?
A metal has a body-centered cubic crystal structure. The density of the metal is 5.96 g/cm3. Find the volume of the unit cell if the atomic mass of metal is 50.
An element (atomic mass 100 g/mol) having bcc structure has unit cell edge 400 pm. The density of element is (No. of atoms in bcc, Z = 2).
Gold has a face-centered cubic lattice with an edge length of the unit cube of 407 pm. Assuming the closest packing, the diameter of the gold atom is ____________.
The empty space in the body-centered cubic lattice is ____________.
The number of atoms contained in a fcc unit cell of a monoatomic substance is ____________.
Which of the following metal(s) show(s) hexagonal close-packed structure (hcp) and which show face-centered cubic (fcc) structure?
Edge length of unit cell of chromium metal is 287 pm with a bcc arrangement. The atomic radius is of the order:
An element with atomic mass 100 has a bcc structure and edge length 400 pm. The density of element is:
Match the type of unit cell given in Column I with the features given in Column II.
| Column I | Column II |
| (i) Primitive cubic unit cell | (a) Each of the three perpendicular edges compulsorily have the different edge length i.e; a ≠ b ≠ c. |
| (ii) Body centred cubic unit cell | (b) Number of atoms per unit cell is one. |
| (iii) Face centred cubic unit cell | (c) Each of the three perpendicular edges compulsorily have the same edge length i.e; a = b = c. |
| (iv) End centred orthorhombic cell | (d) In addition to the contribution from unit cell the corner atoms the number of atoms present in a unit cell is one. |
| (e) In addition to the contribution from the corner atoms the number of atoms present in a unit cell is three. |
The correct set of quantum numbers for 3d subshell is
The coordination number for body center cubic (BCC) system is
The correct set of quantum numbers for 2p sub shell is:
Percentage of free space in body centred cubic unit cell is
If a represents the edge length of the cubic systems, i.e. simple cubic, body centred cubic and face centered cubic, then the ratio of the radii of the sphere in these system will be:-
A solid is formed by 2 elements P and Q. The element Q forms cubic close packing and atoms of P occupy one-third of tetrahedral voids. The formula of the compound is ______.
An element A (Atomic weight = 100) having bcc structure has a unit cell edge length 400 pm. The number of atoms in 10 g of A is ______ × 1022 unit cells.
The ratio of number of atoms present in a simple cubic, body-centred cubic and face-centred cubic structure are, respectively ______.
