Test: Ionic Bonds & Fajans' Rule - JEE MCQ

Cs is electropositive element hence, it forms Cs+ ion. Hence, no covalent bonding.

Cs⁺ has stable inert gas configuration thus, Cs³⁺ is not formed.

Smaller the IE of Mg, easier the formation of Mg²⁺.
Greater the EA of O, easier the formation of O2^-.

KCI is an ionic compound. Force of attraction (F) between K+


Greater the value of D, smaller the value of F, hence larger the solubility.
Note D for CH₃OCH₃ is least out of given solvents, thus solubility is minimum.

Mg(1s² 2s² 2p⁶3s²) is an electropositive element and Cl(1s² 2s² 2p⁶ 3s² 3p⁵)is an electronegative element.

Mg²⁺ attains stable inert gas configuration.


Cl^- also attains stable inert gas configuration.

Al³⁺ attains stable inert gas configuration. 

O^2- attains stable inert gas configuration.

(Three electrons extra than octet, it can donate three electrons)

(Three electrons short of octet, it can gain three electrons) 
Thus, M³⁺ Z^3-
Compound is MZ,

IV. Electrostatic force of attraction between  and
V. H₂O molecules joined together by dipole-dipole interaction.
VI. Outer H₂O molecule joined to by ion-dipole interaction.

By Fajans rule,
Smaller the size of cation, larger the size of anion. Larger the charge on cation or anion, larger the polarising power and thus, greater the covalent nature.

Like dissolves like. Polar solvents (as H₂O) dissolve polar compounds (ionic compounds) and non-polar solvents (as ether) dissolve non-polar compounds (covalent compounds).
By Fajans’ rule smaller the size of cation, larger the size of anion. Larger the charge on cation or anion then larger the polarising power and thus, larger the covalent nature and thus, solubility in non-polar solvents.

By Fajans' rule,
Smaller the size of cation, larger the size of anion. Larger the charge on cation or anion, larger the polarising power and thus, greater the covalent nature.
NaF, Na₂O, Na₃N, Na⁺ is same.

By Fajans' rule,
Smaller the size of cation, larger the size of anion.
Larger the charge ord-electrons present, then larger the polarising power of cation and larger the covalent nature and smaller the solubility in water.

Cu²⁺ due to shielding effect causes more screening than Zn²⁺.
Thus, polarising power of Na⁺ <Zn²⁺ < Cu²⁺ hence, ionic nature and solubility in water is in order
CuS < ZnS < Na₂S

Based on Fajans' rule,
Smaller the size of cation, larger the size of anion, larger the charge,
d-f-Aelectrons present then larger the polarising power, larger the covalent nature and larger the lattice energy.

By Fajans’ rule,
Smaller the size of cation, larger the size of anion, larger the charge, then larger the polarising power, larger the covalent nature, means low melting point.
Smaller the ionic nature, means low melting point 


Hence, most stable is LiF.

By Fajans’ rule, smaller the size of cation, larger the size of anion, larger the charge on cation or anion,
d- and f-electrons present on the ion then greater the polarising power of the ion to polarise the other ion, thus larger the covalent nature.

Thus, com pound with Si⁴+ (smallest cation) and C^4- (largest anion) will be most covalent.

Polarising power of Li⁺ > Na⁺ and AI³⁺ > Na⁺
Thus, LiCI and AICI₃ have covalent nature and extracted into ether.
CuCI due to d-electrons has covalent nature. (Polarising power of Cu⁺ > Na⁺).
Thus, only NaCI (ionic) remains in water.

Cu⁺ = [Ar] 3d¹⁰, Cu⁺ has inner 18-electrons shell. Shielding effect is decreased. Thus, electronegativity is increased. This results in greater polarising power of Cu⁺ .
Hence, CuCI is covalent.

Born Haber cycle involves

(a) In SbF₅ (expansion of octet from 5 to 10 and further to 12).
(b) NH₃, BF₃ both have complete octet. NH₃ is electron rich, donates lone pair to BF₃.
(c) AICI₃ is electron deficient, accepts lone pair from Cl^-.
(d) In SF₄, expansion of octet from 8 to 10 and further to 12.

A → A⁺ + e^- is favourable since, IE of A is low.
B + e^- → B^- is favourable since, EA of B is high.
Thus, A⁺B^- is favoured by low IE of A and high EA of B.

Thus, ionic strength becomes 8 times.