CBSE Class 12 Chemistry - Coordination Compound Notes and Questions

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CBSE Class 12 Chemistry Questions and basic easy to learn concepts/ notes Database for chapter Solid State. Based on CBSE and CCE guidelines. The students should practice these Questions to gain perfection which will help him to get more marks in CBSE examination. Based on CBSE and CCE guidelines. The preparation should be in a manner which helps the students to concentrate more in areas which carry more marks. Please refer to more CBSE Class XII sample papers, question papers, HOTs etc in other links.

 

UNIT 9: CO-ORDINATION COMPOUND

   The compounds which contain dative bonds between metal atom and surrounding species is called co-ordination compounds .The branch of inorganic chemistry which deals with hte study of preparation properties of coordination compound is called co-ordination chemistry.

 K4[Fe(CN)6],    [CuNH3)4]SO4

 

POINTS TO REMEMBER:

 

1.Coordination compounds

Coordination compounds are compoundin which a central metal atom or ion  is linked to a

number of ions or neutral molecules bcoordinate bonds or which contain complex ions. Examples- K4[Fe(CN)6]; [ Cu(NH3)4]SO4; Ni(CO)4

 

2.The main postulates of Werners theory of coordination compounds

 

i) In coordination compoundmetalshow two types of linkages or valencies- Primary and Secondary.

iiThe primary valencies are ionisable and are satisfied bnegative ions.

iiiThe secondary valencies are non- ionisable and are satisfied bneutral molecules or negative ionsThe secondary valence is equal to the C.N and is fixed for a metal.

iv) The ions or groups bound bsecondarlinkages to the metal have characteristispatial arrangements corresponding to different coordination nos.

3.Difference between a double salt and a complex

 

Both double salts as well as complexes are formed by the combination of two or more stablcompounds in stoichiometriratio. However, double salts such as carnallite, KCl.MgCl2.6H2O, Mohrsalt, FeSO4.(NH4)2SO4.6H2O, potash alumKAl(SO4)2.12H2O, etc. dissociate into simplions completely when dissolved in waterHowever, complex ionsuch as [Fe(CN)6]4 of K4[Fe(CN)6] do not dissociate into Fe2+ and CN–  ions.

 

 

IMPOTANT TERMINOLOGY

 

 (i) Coordination entity It constitutes the central metal ion or atom bonded to a fixed number of ions or molecules represented within a square bracket.

 

(ii) Central atom/ ion: In a coordination entity, the atom/ion to which a fixed number of ions/groups are bound in a definite geometrical  arrangement around it, is called the central atom or ion.

 

iii) Ligands: The neutral or negative ions bound to the central metal or

 

ion in the coordination entityThese donate a pair/s of electrons to the central metal atom /ion. Ligands may be classified as-

 

a)         Monodentate/Unidentate: Ligands bound to the central metal atom/ion through single donor atom. Ex- Cl ; H2O ; NH NO2-.

b)         Didentate: Ligates through two donor atoms. Ex- C2O 2- (ox)H2NCH2CH2NH2(en)

c)         Polydentate which ligates through two or more donor atompresent in a single ligandEx- (EDTA)4-

d)         Chelating ligands Di- or polydentate ligands tha uses two or more donor atoms to bind to a single metal ion to form ring- like complexes. (Ox)(edta)

e)         Ambidentate ligand: A ligand  that can ligate through two different atoms, one at a time. Ex-NO2- ; SCN-

v)         Coordination number: The no. of ligand donor atoms to which the metal is directlbonded through sigma bonds onlyIt is commonly 4 or 6.

vi)        Counter ions: The ionisable groupwritten outside the square bracket. Ex- K+ in

K4[Fe(CN)6] OR 3Cl in [Co(NH3)6]Cl3

vii)       Coordination Polyhedron: The spatial arrangement of the ligand atomwhich are directly attached to the central metal atom/ion. They are commonlOctahedralSquare-planar or Tetrahedral

Oxidation numberThe charge that the central atom would carry if all the ligands are

removed along with their pairs of electrons shared with the central atomIt irepresented iparenthesis.

 

viii)      HomolepticomplexesComplexein which a metal is bonded to only onkind of donor groups. Ex- [Co(NH3)6] 3+

 

ix)        HeterolepticomplexesComplexes in which a metal is bonded to more than one kind of donor groups. Ex- [Co(NH3) Cl2]+

 

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