To determine the incorrect statement, let's analyze each option:$\newline$Option 1: Actinoid contraction is greater for element to element than Lanthanoid contraction.$\newline$• Actinoid contraction refers to the gradual decrease in ionic radii of actinoid elements with increasing atomic number.$\newline$• This contraction is indeed greater than lanthanoid contraction due to the poor shielding effect of 5f electrons compared to 4f electrons.$\newline$• Therefore, this statement is correct.$\newline \newline$Option 2: Most of the trivalent Lanthanoid ions are colorless in the solid state.$\newline$• Trivalent lanthanoid ions typically exhibit colors due to f-f electronic transitions.$\newline$• These transitions are allowed due to the partially filled 4f orbitals.$\newline$• Hence, most trivalent lanthanoid ions are not colorless, making this statement incorrect.$\newline \newline$Option 3: Lanthanoids are good conductors of heat and electricity.$\newline$• Lanthanoids, being metals, generally have good electrical and thermal conductivity.$\newline$• This is due to the presence of delocalized electrons.$\newline$• Therefore, this statement is correct.$\newline \newline$Option 4: Actinoids are highly reactive metals, especially when finely divided.$\newline$• Actinoids are indeed highly reactive, particularly in their finely divided form.$\newline$• This reactivity is due to their large atomic and ionic sizes and the presence of unpaired electrons.$\newline$• Thus, this statement is correct.$\newline \newline$Based on the analysis, the incorrect statement is Option 2.