[Boxxxed]

Trends from Ca to Zn

First ionic radii decreases through increasing
number of protons into the
core during filling of the d-orbitals

Then increase because electrons
of d-orbitals enter the electron core
and better shielding of the
4s electrons from attraction of the
protons in the core.
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What does he mean when he says electrons of d-orbitals enter electron core? d-electrons enter the 4s orbital? But there have been electrons there all along.
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Decrease in ionic radii
= decrease in coordination number
= increase in covalency

Why does decrease in ionic radii increase covalency?

Why do the lanthanide elements decrease in ionic radii while the rows above it ultimately end up increasing? Why are f orbitals less shielded from the core than s orbitals?

[JustinCh3m]

Either google or look up in your textbook the term: "lanthanide contraction."

Although this doesn't address all of your concerns, you will find it extremely helpful regarding this topic...