Radius Ratio Rules — Prelims Questions

If the radius of a cation ($r_c$) is $75,\text{pm}$ and the radius of an anion ($r_a$) is $180,\text{pm}$, what coordination number and geometry would be predicted for an ionic compound formed by these ions according to the Radius Ratio Rule?

Which of the following statements about the Radius Ratio Rule is INCORRECT?

For an ionic crystal with a radius ratio ($r_c/r_a$) of $0.200$, which coordination number and geometry would be most stable?

In a CsCl type structure, the coordination number of both $Cs^+$ and $Cl^-$ ions is 8. Which of the following radius ratio ranges is consistent with this observation?

Which of the following ionic compounds is most likely to adopt an octahedral crystal structure based on typical ionic radii?

The limiting radius ratio for tetrahedral coordination is $0.225$. This value is derived assuming that: