D BLOCK ELEMENTS, Summaries of Chemistry

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D BLOCK ELEMENTS

Presented By

Dr.T.VARA PRASAD,

HOD,

Department of Chemistry,

P.R.Government College (A),

Kakinada

Synopsis:

Definition of D-Block elements Transition elements. General and Physical properties of elements Atomic & Ionic size Ionization Enthalpy Oxidation states Coloured ions Catalytic properties Magnetic properties Formation of complex compounds Formation of interstitial compounds

} d-block elements:

The elements of periodic table belonging

to group 3 to 12 are known as d-Block

elements. because in these elements last

electron enters in d sub shell or d orbital.

} The d -block elements lies in between s- and

p-block elements in the long form of

periodic table

Definition of d-block elements

Group 7 Presentation

GENERAL & PHYSICAL PROPERTIES OF D-BLOCK ELEMENTS

Ø PHYSICAL PROPERTIES

Ø ATOMIC & IONIC SIZE Ø IONIZATION ENTHALPY Ø OXIDATION STATES OF D-BLOCK ELEMENTS Ø COLOURED IONS Ø CATALYTIC PROPERTIES Ø MAGNETIC PROPERTIES Ø FORMATION OF COMPLEX COMPOUNDS Ø FORMATION OF INTERSTITIAL COMPOUNDS

ATOMIC & IONIC SIZE

Ø Along the rows nuclear charge increases but the penultimate d-sub shell has poor shielding effect so atomic and ionic size remain almost same.

Ø The radii of the third (5 d) series are virtually the same as those of the corresponding members of the second series.

¢ This phenomenon is associated with the intervention of the 4 f orbital, the filling of 4f before 5 d orbital results in a regular decrease in atomic radii called Lanthanoid contraction which essentially compensates for the expected increase in atomic size with increasing atomic number.

¢ The net resultof the lanthanoid contraction is that the second and the third d series exhibit similar radii (e.g., Zr 160 pm, Hf 159 pm)

¢ Due to an increase in nuclear charge which accompanies the filling of the inner d- orbitals , There is an increase in ionization enthalpy along each series of the transition elements from left to right.

¢ However, many small variations occur.

• Transition elements have variable oxidation states ,due to very small energy difference between (n-1)d & ns sub-shell electrons from both the sub-shell take part in bonding

oxidation states

Most of the transition metal compounds (ionic as well as covalent) are coloured both in solid state & in aqueous state.

Generally the elements/ions having unpaired electrons produce coloured compound.

COLOURED IONS

Scandium oxide

Vanadyl Sulphate dihydrate

Titanium oxide sodium chromate (^) Potassium ferricyanide

Nickel(II) nitrate hexa- hydrate

Zinc sulfate Hepta- hydrate

Mangnaese(II) chloride tetrahydrate

Cobalt(II) chloride Copper(II)sulfate penta- hydrate