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# Which has maximum polarising power in cation? Option:A.$L{i^+}$B.$A{l^{3+}}$C.$M{g^{2+}}$D.$O^{2-}$

Last updated date: 21st Jul 2024
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Hint: By convention, the electron's charge is regarded as negative. By convention, an ion's negative charge is equal to and opposite that of charged proton(s) called positive. An ion's net charge is non-zero since its total number of electrons is greater than its total number of protons.

Because of their opposing electric charges, cations and anions bind each other and readily form ionic compounds. A cation is a positively charged ion with less electrons than protons, while an anion is negatively charged with more electrons than protons.
In electrolysis, a cation is a positively charged ion that is attracted to the cathode.
The potential of a cation to draw the electron cloud towards itself is known as polarising power. The force of polarisation is proportional to the charge/size.
The polarising potential of a cation increases as the size of the cation decreases, while the polarisability of anions decreases as the size of the cation increases. A cation's polarising potential increases as its charge increases, while an anion's polarisability increases as its charge increases.
Among the 4 given options O²⁻is anion.
Now among the other 3 options
The polarising power of a cation increases as the cation's size decreases, while anions' polarisability decreases as the cation's size increases.
Al has the highest charge +3
Hence, Al has the highest polarising power.
The degree of polarisation will be increased if:
The cation has a high charge and is limited in dimension.
Potential ionic.
The anion has a high charge and a large scale.
An anion's polarizability is proportional to the deformability of the electron cloud (i.e. its "softness")
An electron structure with an unfinished valence shell.
The cation's noble gas structure results in better shielding and less polarising strength.

Option B is correct.

Note:
Fajans' laws, established by Kazimierz Fajans in 1923, are used in inorganic chemistry to predict whether a chemical bond would be covalent or ionic. They are based on the charge on the cation as well as the relative sizes of the cation and anion.