Use what you learned in lab about atoms in cubic structures to answer the follow

Question

Use what you learned in lab about atoms in cubic structures to answer the following questions about a solid whose crystal structure was found to have atoms "A" in face sites and "B" in the edge and center sites of a cubic unit cell.

How many "A"s are there in a unit cell?

How many "B"s are there in a unit cell?

What is the correct chemical formula for this solid?

Use what you learned in lab about atoms in cubic structures to answer the following questions about a solid whose crystal structure was found to have atoms "C" in corner sites and "D" in the edge sites of a cubic unit cell.

How many "C"s are there in a unit cell?

How many "D"s are there in a unit cell?

What is the correct chemical formula for this solid?

Explanation / Answer

1) in this unit cell A is present at all the face centered places.

one face center shared with 2 unit cells , so for 6 x 1/2 = 3 atoms of A present in unit cell.

b atoms present at all edge centers total 12 edges each edge shared with 4 unit cells.

so total atoms 12 x 1 / 4= 3 atoms at edge center

and one atom at center. sotal b atoms = 3+ 1 = 4 atoms of B

chemical formula is A3B4.

2) in unit cell one corner is shared with 8 corners total 8 corners.

number of C atoms = 8 x 1 /8 = 1 atom of C

total d atoms = 12 x 1 /4 = 3 atoms of D

formula of compound is CD3

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