Explanation
Percent ionic character of a covalent bond depending on the electronegativity difference.
∴ Percentage ionic character = 16(XA – XB) + 3.5(XA – XB)2
Where XA and XB are electronegativities of atoms A and B respectively.
Hence percent ionic character is directly proportional to (XA – XB). Therefore as (XA – XB) increases, percent ionic character will also increase. Therefore the curve C is the correct shape for AB bond.
Polarizing power of cation α charge/size, for Be2+, Mg2+, Ca2+ since charge is same and size is in the order Ca2+> Mg2+> Be2+, the order of polarizing power is
Be2+> Mg2+> Ca2+, charge of K+ is lowest and size is larger than Ca2+.
∴ its polarizing power is lowest.
Hence the correct order is K+> Ca2+> Mg2+> Be2+.
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