Why d-block element form complexes?

Q. Atomic size ___________ in a period due to ______ in nuclear charge.

Q. Statement 1: Lanthanides have much less tendency to form complexes than actinides.
Statement 2: Compared to actinides, the lanthanides have relatively larger size of atoms and less nuclear charge.

Q. As nuclear charge increases, atomic size :

Q. Atomic size across a period increases with increase in nuclear charge of element.

Q. Assertion :Atomic size decreases in a period due to increase of atomic number. Reason: The nuclear charge is increasing and size of valence shell remains same as we move from left to right. Hence, in any period, the atomic size of the element decreases from left to right.