CHEMISTRY- CH8 d and f block

transition elements (dblock) and inner transition elements(fblock)

transition and inner transition elements

d and f block ( doesnt include zn,cd,hg)…. zn cd and hg have fully filled d orbital in their configuration in their ground state as well as oxidised state hence they are not rehgarded as transition elemetnsd

different configurations

1ST SERIES - Cr 3d⁵ 4s¹ and cu 3d¹⁰ 4s¹

2ND SERIES - Nb(41) 5s¹ 4d⁴ till Pd 5s⁰4d¹⁰

^ETC

TYPICAL METALLIC STRUCTURES

ZN

HG THEY HAVE TYPICAL METALLIC STRUCTURES

MN

CD

characterstic prroperties exhibited by d block

#display of a variety of oxidation states, formation of coloured ions and entering into complex formation with a variety of ligands.

#catalytic property and paramagnetic behaviour.

Silver atom has completely filled d orbitals (4d¹⁰) in its ground state. How can you say that it is a transition element?

The outer electronic configuration of Ag (Z=47) is 4d¹⁰5s¹. It shows+1 and + 2 O.S. (in AgO and AgF₂). And in + 2 O.S., the electronic configuration is d⁹ i.e, d-subshell is incompletely filled. Hence, it is a transition element.

PHYSICAL PROPERTIES

#The transition metals (with the exception of Zn, Cd and Hg) are very hard and have low volatility.

#Their melting and boiling points are high.attributed to the involvement of greater number of electrons from (n-1)d in addition to the ns electrons in the interatomic metallic bonding

# melting points of these metals rise to a maximum at d5 except for anomalous values of Mn and Tc and fall regularly as the atomic number increases.

metallic bonding and enthalpy of atomisation

# greater the number of valence electrons, stronger is the resultant bonding.

# enthalpy of atomisation is an important factor in determining the standard electrode potential of a metal, metals with very high enthalpy of atomisation (i.e., very high boiling point) tend to be noble in their reactions

#metals of the second and third series have greater enthalpies of atomisation than the corresponding elements of the first series

In the series Sc(Z = 21) to (Z = 30), the enthalpy of atomisation of zinc is the lowest i.e., 126 kJ mol^-1. Why?

The enthalpy of atomisation is directly linked with the stability of the crystal lattice and also the strength of the metallic bond. In case of zinc (3d¹⁰4s² configuration), no electrons from the 3d-orbitals are involved in the formation of metallic bonds since all the orbitals are filled. However, in all other elements belonging to 3d series one or more d-electrons are involved in the metallic bonds. This means that the metallic bonds are quite weak in zinc and it has therefore, lowest enthalpy of atomisation in the 3d series

Variation in Atomic and Ionic Sizes of Transition Metals

• ions of the same charge in a given series show progressive decrease in radius with increasing atomic number.

• shielding effect of a d electron is not that effective, hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases.

• the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin.

• The filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contractionr. The net result of the lanthanoid contraction is that the second and the third d series exhibit similar radii (e.g., Zr 160 pm, Hf 159 pm) and have very similar physical and chemical properties

• REASON the shielding of one 4f electron by another is less than that of one d electron by another, and as the nuclear charge increases along the series, there is fairly regular decrease in the size of the entire 4f n orbitals.

DENSITY

The decrease in metallic radius coupled with increase in atomic mass results in a general increase in the density of these elements. Thus, from titanium (Z = 22) to copper (Z = 29) the significant increase in the density may be noted

Why do the transition elements exhibit higher enthalpies of atomisation?

Because of large number of unpaired electrons in their atoms they have stronger interatomic interaction and hence stronger bonding between atoms resulting in higher enthalpies of atomisation