In condensed matter physics and inorganic chemistry the cation-anion radius ratio (also: radius ratio rule) is
the ratio of the ionic radius of the cation to the ionic radius of the anion in a cation-anion compound.
What is radius ratio rule write its importance?
The ratio of the radius of cations (r
+
) to the radius of the anion (r
–
) is known as the radius ratio of the ionic solid. The significance of radius ratio: It
is useful in predicting the structure of ionic solids
. … Greater the radius ratio, greater is the coordination number of cations and anions.
What is the formula of radius ratio?
Radius Ratio refers to as the ration of smaller ionic radius (cation) by the ratio of larger ionic radius (anion). Hence,
Radius ration ρ = r
s
/r
l
.
What is radius ratio rule what are its limitations?
Although radius is a useful concept of determining coordination number and in understanding the structure of ionic compounds yet there are a few limitations to this rule. (i)
Each ion is considered as a hard sphere for determining the optimum arrangement of ions in the crystal lattice
.
What is the radius ratio How can to predict the structure of an ionic crystal with the help of RF?
| Radius ratio Coordination number Geometry of holes (voids) | 0.414-0.732 6 octahedral | 0.732-1.00 8 cubic |
|---|
What is the ratio of ions?
| Ion Percent in Seawater Percent in Blood | Na + 2.36 0.322 | Cl − 1.94 0.366 | Mg 2 + 0.13 0.002 | SO 4 2 − 0.09 — |
|---|
What do you mean by radius ratio What is its application?
The
ratio of the radius of the smaller ion to that of the larger; commonly cation to anion
. Radius ratios are used to predict coordination numbers of anions about cations in ionic crystal structures.
What is a large charge radius ratio?
Polarization will be increased by high charge and small size of the cation. Thus, larger the ratio of charge and radius, higher is
the polarization power of the cation
, more is the covalent character in the compound and lesser is the ionic character; Ionic compounds are more stable when exposed to heat.
What is the radius ratio of caf2?
Calcium fluoride occurs naturally as the mineral fluorite. The ionic radius of the calcium ion is 1.26 Å and that of the fluoride ion is 1.17 Å. In this case the cation is the larger ion, and the ratio of radii for the anion and cation is
r
–
/r
+
= 1.17/1.26 = 0.929
.
What is the radius ratio of tetrahedral void?
Radius ratio of Tetrahedral void is
0.225
.
What is the effect of radius ratio on coordination number?
As the radius ratio becomes smaller than this,
triangular coordination becomes the stable configuration
. For triangular coordination, the coordination number is three, that is 3 anions surround the smaller cation. The “no rattle” limit is reached for triangular coordination when Rx/Rz becomes less than 0.155.
What are the limitation of radius ratio rule and coordination number?
Limiting radius ratio
is 0.524
, therefore coordination number is six and shape is octahedral.
What is the radius ratio of CsCl?
The radius ratio in CsCl is
0.93
.
What is the coordination number of NaCl?
In NaCl crystal, each sodium ion is surrounded by
6
chloride ions and each chloride ion is surrounded by 6 sodium ions. So, the coordination number of NaCl as per definition will be 6:6.
