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4. Fajans' rule states that a compound with low positive charge, large cation and small anion has ionic bond where as a compound with high positive charge, small cation and large anion are covalently bonded. For high charge, small cation will have more polarizing power. Where as larger is the size of anion, more will be the polarization of anion.
Nov 5, 2017 · So, between $\ce{Ag^+}$ and $\ce{Ca^2+}$, Fajan's rule will be much more applicable to the silver halides as the silver cation will generate much more polarization as compared to $\ce{Ca^2+}$. As to your question about when to apply which concept: You are basically required to compare the sum of the hydration enthalpy and lattice enthalpy.
May 2, 2021 · 1 2. 1. These classifications are made by us and not by nature and whenever we humans do so there is always ambiguity regarding the borderline from which you can say that type of bind has changed. Rules like Fajan's rule help us the covalent character in different ionic bonds. Rules like this cannot tell you if something is too covalent to not ...
Somtimes, like in your question, both the factors support each other. Sometimes, when they are opposite, like in the case of $\ce{LiF}$ and $\ce{NaCl}$, it is tough to determine relative covalency using Fajan’s rule.
Apr 13, 2018 · Source 2. But it we are asked to compare the ionic character of hydrides (LiH, NaH, KH, RbH, CsH), we can not use the Fajan's rule. This is because, here the anion is very small (HX− H X −) as compared to the cations (alkali metal cations). The ionic character is this case can thus be compared on the basis of Lattice energy.
Oct 4, 2022 · He said that if we another example with alkaline earth metals, then ideally according to Fajan's rule BaSO4 should be more soluble than MgSO4. But this is not the case because as we go down the group the decrease in hydration energy is greater than the decrease in lattice energy and thus solublity decreases.
Jan 12, 2020 · Violation of Fajans' rule. According to Fajans' rules, greater charge in an ionic compound results in more covalent character. But why is it that sodium oxide is more covalent than magnesium oxide? Google says boiling point of magnesium oxide is more than sodium oxide.
Aug 25, 2021 · Fajan's rule along with size compatibility and polarization decides the ionic character of a compound. By Fajan's rule we have: covalent character directly proportional to the extent of polarization, implying that the smaller cation will cause greater distortion of electron cloud as compared to the larger cation.
Oct 28, 2015 · Whether to use Fajan's rule or to go according to the periodic trend. One way we can say as the distance between ions increases bond strength decreases and hence melting point decreases. But then according to Fajan's rule the charge density over RbCl is least and hence covalent character would be minimum and hence melting point should be maximum. :/ $\endgroup$
Mar 27, 2024 · First and foremost, hydrides of alkali metals are ionic in nature. So, you cannot use Fajan's rule to determine ionic character as it is only used for covalent compounds. For ionic compounds we use something called cation-anion radius ratio RC/RA (C = cation, A=anion). For small cations like $\ce{Li+}$, small anions like $\ce{H-}$ are preferred ...
