Question

If the radius ratio is between 0.414 - 0.732, what will be the type of void present? What will be the coordination number?

• A. Tetrahedral - 4
• B. Linear - 2
• C. Octahedral - 6
• D. Cubic - 8

Answer 1

The correct option is C

Octahedral - 6

Remember the derivation we saw? In this context we calculate the radius ratio of the ions that make up the crystal assuming they have an octahedral void and we end up with this number. Since the converse is also true, we say that this radius ratio gives rise to octahedral void. So, when the radius ratio is 0.414 - 0.732, the type of void is octahedral. Add this to your memory. And we know that when we have octahedral voids, there will be 6 surrounding particles - atoms or ions. Coordination number will therefore be 6.