Which of the following statement(s) is (are) true?
$\text{P)\hspace{0.17em}Ionisation\hspace{0.17em}energ}\propto \frac{1}{\text{Screening\hspace{0.17em}effect}}$
Q) The ionization energies of Be and Mg are more than ionization energies of B and Al respectively
R) Atomic and ionic radii of Niobium and Tantalum are almost same
S) Metallic and covalent radii of potassium are $2.3\text{Å}$   and $2.03\text{Å}$  respectively

: Metallic radius is greater than the covalent radii. 
${\text{I.E}}_{\text{1}}{\text{\hspace{0.17em}of\hspace{0.17em}Be\hspace{0.17em}\hspace{0.17em}>\hspace{0.17em}I.E}}_{\text{1}}{\text{\hspace{0.17em}of\hspace{0.17em}B : I.E}}_{\text{1}}{\text{\hspace{0.17em}of\hspace{0.17em}Mg\hspace{0.17em}\hspace{0.17em}>\hspace{0.17em}I.E}}_{\text{1}}\text{\hspace{0.17em}ofA}l$
This is due to earlier element has half filled configuration than later element in the same period.
$$\begin{gathered} \text{Nb\hspace{0.17em}}\left(\mathrm{Z}=41\right)\to {\text{\hspace{0.17em}5}}^{\text{th}}\text{\hspace{0.17em}period\hspace{0.17em}\& 4d-block element} \\ \text{Ta\hspace{0.17em}}\left(\mathrm{Z}=73\right)\to {\text{\hspace{0.17em}6}}^{\text{th}}\text{\hspace{0.17em}period\hspace{0.17em}\& 5d-block element} \end{gathered}$$ 
Due to lanthanide contraction by the intervene of 4f  sub shell, both 4d and 5d block elements have almost same atomic radii