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Suggest a possible reason for the following observations : (i) In the solid state, PCl_(5) behave as an ionic species. (ii) H_(2)S is more acidic than water. (iii) Fluorine forms the largest number of interhalogen compounds amongst the halogens. |
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Answer» Solution :(i) In solid state `PCl_(5)` BEHAVES as an ionic species : Because of the formation of `(PCl_(4))^(+) and (PCl_(6))^(-)` in which cation is `(PCl_(4))^(+)` is tetrahedral and anion `(PCl_(6))^(-)` octahedral. (ii) `H_(2)S` is more acidic than water : Because `H_(2)S` has lower bond dissociation energy than `H_(2)O` bond. (iii) Largest no. of interhalogen compounds are formed by fluorine due to its smaller size and higher electronegativity. State decreases down the group due to increase in size and metallic character. Bi (last member of the group) hardly forms any compound of `-3` oxidation state. The stability of `+5` oxidation state decreases down the group, whereas that of `+3` oxidation state increases down the group (due to inert PAIR effect). N reacts with oxygen showing `+1, +2, +3,+4 and +5` oxidations states. P shows `+1 and +4` oxidation states in some oxo - acids. (iii) Atomic size :Covalent and ionic radii (in a particular state) increase down the group. From N to P, covalent radius increase considerable. From As to Bi, there is only a small increase in covalent radius. The REASON is the presence of completely filled d - and /- or /f orbitals in heavier members. (iv) Ionization enthalphy : Ionization enthalpy decreases down the group due to gradual increase in atomic size. I.E., of group - 15 elements is greater than that of group - 14 elements and group - 16 elements in thecorresponding periods. |
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