As we move across a period of the periodic table, why do the sizes of the transition elements change more gradually than those of the representative elements?
Solution Step 1 The size of the representative elements decrease markedly but the size of the transition elements decrease only slightly as we move from left to right in a period. Explanation Let us take the example of first row transition elements. All the first-row transition elements have 4s orbital as the outermost occupied orbital. The atomic radius will depend on the strength of the nuclear charge felt by the 4s electrons. The greater the nuclear charge, smaller would be the atom. As we move from scandium to copper electrons are being added to an inner 3d subshell.The effective nuclear charge experienced by the outermost electrons depends on the shielding provided by inner electrons.The d electrons are less efficient in shielding when compared to the s or p electrons and thus the shielding effect felt by the valence electrons would be less. So the size of the transition elements will decrease gradually when compared to representative elements.