shielding of one f 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 f n orbitals. 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 = ) to copper (Z = ) the significant increase in the density may be noted (Table . ).
Sc Ti Cr Mn Fe Co Ni Cu Zn Y Zr Nb Mo Tc Ru Rh Pd Ag Cd La Hf Ta W Re Os Ir Pt Au Hg Radius/nm Fig. . : Trends in atomic radii of transition elements Atomic number Electronic configuration 4s 4s 4s 4s 3d 4s 4s 4s 4s 4s 4s + 4s 4s 4s 4s 4s 4s 4s 4s [Ar] Enthalpy of atomisation, D a H o /kJ mol – Ionisation enthalpy/ DDDDD i H o /kJ mol – D i H o I D i H o II D i H o III Metallic/ionic radii/pm Standard electrode + /M – . – .
– . + . - . potential E o /V + /M – .
. . . Element Sc Ti Co Ni Cu Zn Table .
: Electronic Configurations and some other Properties of the First Series