Why do transition metal atomic radii increase after nickel?

[sciencenerd]

Could anybody help me with this?

The atomic radii of the transition metals show some anomaly in their atomic radii as
compared to those elements in Group 1A-7A, which generally shows a decrease as one
goes from left to right in a period. The atomic radii of the transition metals decrease as
do those in Groups 1A-7A, but then they increase. For example, Sc has an atomic radius
of 162 pm and the atomic radii decrease until Ni to 124 pm, but Cu an Zn have larger
atomic radii than Ni and Zn is even larger than Cu. How do you explain this?

 

[Drik Paul]

Sciencenerd,
It is due to the repulsion between the electrons of the shells which increases the atomic radius due to the increase in the charge