Account for the following:
(B) In case of transition elements, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number.
When the number of electrons in an atom is high, as in transition elements, the inner electrons ‘shield’ the outer electrons from the nuclear force of attraction. This is known as the shielding effect .
The shielding effect in d-orbital is very poor due to its low electron density.
Hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases .