Basic and Fundamental of d-Block elements

1. Mr.Halavath Ramesh
16-MCH-001
Dept. of Chemistry
Loyola College
University of Madras-Chennai

2. The d-Block elements are found in the middle of the periodic table. The d-Block elements
are called Transition metals and have valence electrons in the d-orbital. The d-Block elements are
found in groups 3,4,5,6,7,8,9,10,11 and 12 of the periodic table. There are 40 d-Block elements. The
d-orbital is filled with the electronic shell”n-1”. The f-block elements are also called as inner
transition elements. They are : lanthanides and Actinides. Not all d-block elements count as transition
metals. A transition metal is one which forms one or more stable ions which have incompletely filled
d-orbital. On the basis of this definition scandium and Zinc do not count as transition metals even
through they are members of the d-block.
Properties of Transition Elements:
1.have large charge / radius ratio. 2. Are hard and have high densities. 3. Have high melting and
Boiling point.4. From compounds which are often paramagnetic. 5. Show Variable Oxidation states.6.
Form colored ions and compounds.7. Form compounds with profound catalytic activity. 8.Form stable
complexes.

6. In the modern periodic table elements are classified into four types based on electronic configuration
1. S-block elements
2. P-block elements
3. d- block elements
4. f- block elements
The elements whose differentiating electrons enter into (n-1)d sub-level are called d-block
elements. The d-block elements in which the atoms or ions having incomplete d-orbitals are called
transition elements. A typical transition element shall have an incompletely filled d-sub level either
in its elementals form or in any of its chemically significant oxidation state. Therefore all d-block
elements are not true transition elements
e.g. Zn , Cd, and Hg
Exceptional Configuration of Some d-block elements:
** The elements with exceptional configuration in 3d series are
Cr(24) ……[Ar] 3d5 4s1
Cu(29)……[Ar] 3d10 4s1

7. Crystal Field Theory (CFT)
Crystal Field Theory (CFT) describes the breaking of degeneracy's of electron orbital state usually d or f orbital's due
to a static electric field produced by a surrounding charge distribution (anion neighbors).This theory has been used to
describe various spectroscopes of transition metal coordination complexes in particular optical spectra (colors).
According to the crystal field theory the interaction between a transitions metal and ligands arises from the attraction
between the positively charged metal cat ions and the negatively charge on the non-bonding electrons of the ligands.
The electron in the d-orbitals and those in the Ligand repel each other due to repulsion between like charges. Thus the
d-electrons closer to the ligands will have a higher energy than those further away which results in the d-orbitals
splitting in energy .This splitting is affected by the following factors.
1.The Nature of the metal ion.
2. The metal oxide state .A higher oxidation state leads to a larger splitting relative to the spherical field.
3. The arrangement of the ligands around the metal ion.
4.The co ordination number of the metal (i.e., tetrahedral ,octahedral).
5. The nature of the ligands surrounding the metal ion. The stronger the effect of the ligands then the greater the
difference between the high and low energy d groups.