InterviewSolution
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InterviewSolution
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What arethe salientfeatures of valence bond theroy (VBT) ? |
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Answer» Solution :The sailent feature of valencebond theory (VBT) are asfollows: (1) Accoridingto thisthory ,a centrealmetal atomor ionpresentin a complex provides a definite NUMBEROF vannct orbitals(s,p , d and f)to commodate the electrons from the LIGANDS fortheformationcoordinatebonds with themetal ion / atom. (2) The number of vacant orbitals provided by the central metal atom or ion is the same as the coordination number of the metal. For example: `CU^(2+)` provides 4 vacant orbitals in the complex, `[Cu(NH_(3)_(4)]^(2+)`. (3) The vacant orbitals of metal atom or ion undergo hybridisation forming the same number of hybridised orbitals, since the bonding with the hybrid orbitals is stronger. (4) Each ligand has ONE or more orbitals containing one or more lone pairs of the electrons. (5) A coordinate bond is formed by the overlapping of the hybrid orbital of the metal atom or ion with the filled orbitals of the ligands with a lone pair of electrons. (6) Hence each coordinate bond provides two electroms to the central metal atom or ion. (7) Greater the overlapping, the stronger is the coordinate bonds. (8) When inner orbitals namely (n - 1)d-orbitalsin transtitionmetal atomareionhydridise ,the complex is alledinnercomplexand whenouterorbitals i.e.,nd-orbitalshydridisethen thecomplexis calledouter complex. (9) When the central metal atom or ion in the complex contains one or more unpaired electrons the complex is paramagnetic while if all the electrons are paired, the complex is diamagnetic. (10)Strong field ligands like `NH_(3)`, `CN^(-)`, etc. in the complex cause pairing of the unpaired electrons present in the metal atom or ion. This process is called spin pairing process. This changes the magnetic properties of the complex. |
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