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प्रश्न
A cubic solid is made of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body-centre. What is the formula of the compound? What are the coordination numbers of P and Q?
A cubic solid is made up of two elements P and Q. Atoms Q are present at the corners of the cube and atom P at the body centre. What is the formula of the compound?
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उत्तर
It is given that the atoms of Q are present at the corners of the cube.
Therefore, number of atoms of Q in one unit cell = `8 xx 1/8`
= 1
It is also given that the atoms of P are present at the body centre.
Therefore, number of atoms of P in one unit cell = 1
This means that the ratio of the number of P atoms to the number of Q atoms, P : Q = 1 : 1
Hence, the formula of the compound is PQ.
The coordination number refers to the number of nearest neighbouring atoms surrounding a given atom. For P, since it is surrounded by Q atoms, we have:
Coordination number of P = 8
For Q, which is surrounded by P atoms, the coordination number is also:
Coordination number of Q = 8
Thus, the formula of the compound is PQ, and the coordination numbers of both P and Q are 8.
Since the lattice is body-centred cubic, the coordination number of each atom is 8.
Notes
Students should refer to the answer according to their questions.
संबंधित प्रश्न
Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.
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- What is the length of the side of the unit cell?
- How many unit cells are there in 1.00 cm3 of aluminium?
The coordination number of AB having rock salt geometry is ____________.
Hexagonal close packed arrangement of ions is described as ____________.
The arrangement ABC ABC.... is referred to as ____________.
What is the coordination number in a square close packed structure in two dimensions?
In NaCl structure ____________.
Match the type of packing given in Column I with the items given in Column II.
| Column I | Column II |
| (i) Square close packing in two dimensions |
(a) Triangular voids |
| (ii) Hexagonal close packing in two dimensions |
(b) Pattern of spheres is repeated in every fourth layer |
| (iii) Hexagonal close packing in three dimensions |
(c) Coordination number 4 |
| (iv) Cubic close packing in three dimensions |
(d) Pattern of sphere is repeated in alternate layers |
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The right option for the number of tetrahedral and octahedral voids in the hexagonal primitive unit cell is ______.
The right options for the number of tetrahedral and octahedral voids in the hexagonal primitive unit cells is ______.
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The empirical formula for a compound with a cubic close packed arrangement of anions and with cations occupying all the octahedral sites in AxB. The value of x is ______. (Integer answer)
The density of a pure substance 'X' whose atoms pack in cubic close pack arrangement is 1 g/cc. If all tetrahedral voids are occupied by 'Y' atoms. The value of '3a' is ______ g/cc, if the density of resulting solid is 'a' g/cc.
[Given: Atomic mass (X) = 30 g/mol, (Y) = 20 g/mol]
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