Coordination compounds 1

Question 1

define coordination compounds

Answer 1

transition metals
form a large number of complex compounds in which
the metal atoms are bound to a number of anions or
neutral molecules by sharing of electrons. In modern
terminology such compounds are called coordination
compounds.

Question 2

The first to formulate
his ideas about the structures of coordination compounds.

Answer 2

Alfred Werner (1866-1919), a Swiss chemist was the first to formulate
his ideas about the structures of coordination compounds.

Question 3

Werner proposed the term secondary valence for…

Answer 3

Werner proposed the term secondary valence for the
number of groups bound directly to the metal ion; in each of these
examples the secondary valences are six.

Question 4

Werner in 1898, propounded his theory of
coordination compounds. The main postulates are:

Answer 4

1. In coordination compounds metals show two types of linkages
   (valences)-primary and secondary.
2. The primary valences are normally ionisable and are satisfied by
   negative ions.
3. The secondary valences are non ionisable. These are satisfied by
   neutral molecules or negative ions. The secondary valence is equal to
   the coordination number and is fixed for a metal.
4. The ions/groups bound by the secondary linkages to the metal have
   characteristic spatial arrangements corresponding to different
   coordination numbers.

He further postulated that octahedral, tetrahedral and square planar
geometrical shapes are more common in coordination compounds of
transition metals.

Question 5

polyhedra.

Answer 5

In modern formulations, such spatial arrangements are called
coordination polyhedra.

Question 6

Define complexes and counter ions

Answer 6

The species within the square bracket are
coordination entities or complexes and the ions outside the square
bracket are called counter ions.

Question 7

Similarity between a double salt and a complex

Answer 7

Both double salt as well as complexes are formed by the combination of two or more stable compounds in stoichiometric ratio

Question 8

Difference between a double salt and a complex

Answer 8

• double salts dissociate into simple ions completely when dissolved in water.
• complex ions such as
  [Fe(CN)6]4– of K4[Fe(CN)6] do not dissociate into
  Fe2+ and CN– ions.

Question 9

double salt example

Answer 9

carnallite, KCl.MgCl2.6H2O,
Mohr’s salt, FeSO4.(NH4)2SO4.6H2 O,
potash alum, KAl(SO4)2.12H2O