35 Year JEE Previous Questions: The d- and f-Block Elements & Coordination

A square planar complex is formed by hybridisation of   atomic orbitals

The  chemical formula of nitropentammine chromium (III) chloride is

It can exist in following two structures

nitropentammine chromium (III) chloride

Nitropentammine chromium (III) chloride Therefore the type of isomerism found in this compound is linkage isomerism as nitro groupis linked through N as –NO₂ or through O as –ONO.

Compounds that contain at least one carbon metal bond are known as organometallic compounds. In CH₃-Mg-Br (Grignard's reagent) a bond is present between carbon and Mg (Metal) hence it is an organometallic compound.

Common oxidation states of Ce (Cerium) are + 3 and + 4

In lanthanides there is a regular decrease in the atomic radii as well as ionic radii of trivalent ions as the atomic number increases from Ce to Lu. This decrease in size of atoms and  ions is known as lanthanide contraction.
Although the atomic radii do show some irregualrities but ionic radii decreases from La to Lu. Thus the correct order is.

Yb⁺³    <   Pm ⁺³  <    Ce ⁺³ < La ⁺³
86.8pm   97pm     1 02pm  103pm

Mn⁺⁺ –5 unpaired electrons
Fe⁺⁺ – 4 unpaired electrons
Ti⁺⁺ – 2 unpaired electrons
Cr⁺⁺ – 4 unpaired electrons hence maximum no. of unpaired electron is present in Mn⁺⁺.

NOTE : Magnetic moment × number of unpaired electrons

The cyano and hydroxo complexes are far more stable than those formed by halide ion. This is due to the fact that CN^– and OH^– are strong lewis bases (nucleophiles).
Further [Fe(OH)₅]^3– is not formed. hence most stable ion is [Fe(CN)₆]^3-

Let the O. No of Ni in K₄[Fe(CN)₆] be = x then
4 (+ 1) + x + (–1) × 4 = 0  ⇒ 4 + x – 4 = 0 x = 0

When KI is added to mercuric iodide it disssolve in it and form complex.

f-block elements show a regular decrease in atomic size due to lanthanide/actinide contraction.

When a solution of potassium chromate is treated with an excess of dilute nitric acid. Potassium dichromate and H₂O are formed.

AgNO₃ on heating till red hot decomposes as follows :

(n–1)d⁵ns² attains the maximum O.S. of + 7

Grey tin is brittle and crumbles down to powder in very cold climate The conversion of grey tin to white tin is acompained by increase in volume., This is knwon as tin plaque or tin disease.

CN^– ion acts good complexing a s well as reducing agent.

The coor dination number of centr al metal atom in a complex is equal to number of monovalent ligands, twice the number of bidentate ligands and so on, around the metal ion bonded by coordinate bonds.
Hen ce coordin ation number = no. of s bonds for med by metals with ligands

Hybridisation

Hence [ Ni(NH₃)₆]²⁺ is outer orbital complex.

The chlorophyll molecule plays an impor tant role in photosynthesis, contain porphyrin ring and the metal Mg not Ca.

The +4 oxidation state of cerium is also known in solution.

Isomers

NOTE :The greater the number of unpaired electrons, greater the magnitude of magnetic moment. Hence the correct order will be

[MnCl₄]^{– –} > [CoCl₄]^{– –} > [Fe(CN)₆]^4–

Oxidation state of Cr in [Cr (NH₃)₄ Cl₂]+.
Let it be x,  1 × x + 4 × 0 + 2 × (–1) = 1 Therefore x = 3.

2Cu₂O + Cu₂S → 6Cu + SO,
self reduction.

oxidation state of Cr is 3+.

 Hg₂Cl₂ + 2NH₄OH → HgNH₂Cl +NH₄Cl + 2H₂O

NOTE : In vertical columns of transition elements, there is an increase in size from first member to second member as expected but from second member to third member, there is very small chang in size and some times sizes are  same. This is due to lanthanide contraction this is the reason for Zr and Hf to have same radius.