Group 3-12 correspond to the filling of the atomic d-orbital of the second outermost shell with electron configurations

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Group 3-12 correspond to the filling of the atomic d-orbital ofthe second outermost shell with electron configurations rangingfrom s2d 1 to s2d 10. While f-block elements, the forbital isprogressively filled as electrons are added to the atoms. Theproperties of these elements differ from d-block and s-block.
1. A student conducted an experiment by mixing the solution ofmetal ions and ligands. At the end of experiment, colourlesscomplexes were formed. Why the complexes appeared colourless? Namean example of colourless metal complex. [2 Marks]
2. The degree of occupancy in the electronic shells affectthe size of lanthanides and actinides. Briefly explains why thereis a gradual decrease in atomic size from La to Lu with theincreasing of atomic number. [3 Marks]