What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 1/3rd of tetrahedral voids? Number of tetrahedral voids formed = 2 × Number of atoms of element Y Number of atoms of element Y in the ccp unit cell = 4 Number of tetrahedral voids formed = 2 × 4 = 8 Number of tetrahedral voids occupied by atoms of X = (1/3) × 8 = 8/3 Ratio of the numbers of atoms of X and Y = 8/3 : 4=2 : 3 Hence, the formula of the compound is X2Y3. Concept: Crystal Lattices and Unit Cells Is there an error in this question or solution?
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?
Formula of a compound is same as the formula of unit cell. An atom at the corner of cube contributes only l/8th to the unit cell and there are 8 corners in a cube.∴ No. of atoms of Q in the unit cell =8×18 = 1. An atom at centre of cube belongs only to this unit cell and there is only one body centre in the unit cell. ∴ No. of atoms of P in the unit cell = 1 x 1 = 1 Thus, the formula of compound is PQ or QP. For body centred cubic unit cell, the coordination number is 8:8. ∴ Co-ordination number P = 8 and also coordination number of Q = 8. |
What is the formula of a compound in which element y form CCP and atoms occupy two third of octahedral voids?
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