Question

Why do some of the periodic properties like atomic size, electronegativity and ionization potential of transition and inner transition elements not show as much variation as the representative elements ?

Answer 1

The atomic size, ionisation energy and electronegativity of transition elements show regular variation upto middle of the series (upto Mn group), after which as the d electrons are not properly shielded the value becomes almost constant. When we move from 4d series to 5d series (inner transition elements) the difference is not that much pronounced due to Lanthanide contraction. Lanthanide contraction is due to poor shielding of f electrons the attraction between the nucleus and outer electron is strong and the size become less.