Atomic Radii, Ionic Radii and Vanderwall Radii

The metallic radius is half the internuclear distance separating the non-metal cores in the metallic crystal.

Explain the variation of atomic radius in the first transition series.

Covalent radius has a higher value than Van der Waals radius.

The atomic radius increases with increase in number of shells.

Screening factor calculated by using the formula, ${\mathrm{Z}}_{\mathrm{eff}}={\mathrm{Z}}_{\mathrm{actual}}-\mathrm{\sigma }$ is known as _____.

State the Slater's rule for calculating the screening factor.

What is effective nuclear charge? How it changes in a group and a period? 

Cation is smaller than neutral atom and anion a bigger than neutral atom. Why? 

Van der Waals radius is _____ than covalent radius.

Which of the following species have correct order of size?

Along the period $(⟶)$ atomic/ionic radii and metallic character decreases while $IE,EN,$non-metallic character and oxiding power increases. Down the group $(\downarrow ),$ atomic/ionic radii, metallic character and reducing character increases while $IE$ and $EN$ decrease. However, ${{∆}_e}_g{H}^{⊝}$ becomes less negative down a group but more negative along a period.

In which of the following pairs, both species have nearly  the same size?

Along the period $(⟶)$ atomic/ionic radii and metallic character decreases while $IE,EN,$non-metallic character and oxiding power increases. Down the group $(\downarrow ),$ atomic/ionic radii, metallic character and reducing character increases while $IE$ and $EN$ decrease. However, ${{∆}_e}_g{H}^{⊝}$ becomes less negative down a group but more negative along a period.

If the ionic radii of ${\mathrm{M}}^{\oplus }$ and ${\mathrm{X}}^{⊝}$ are about $135 \mathrm{pm},$then expected values of metallic radii of $\mathrm{M}$and $\mathrm{X}$ should be respectively.