Question

why d and f block elements are less electropositive than a group first and second elements

Answer 1

because elements in group 1 and 2 have 1 or 2 electrons in outermost shell so they easily lose electron and become +very charged as compared to d and f block elements

Answer 2

d and f-block elements are in the middle of the periodic table while group 1 and group 2 are on the left side of the periodic table. Electropositive character decrease as we move from left to right in the periodic table. This is because of the increase in ionisation potential as we move along the period.