Who made the idea that as you go down the periodic table the atomic radius increases and the first ionization energy decreases?

The idea that as we go down the periodic table the atomic radius increases and first ionization energy decreases was given by Henry Moosely after he made some changes in the periodic table, the theory proposed by Mendeleev.

Explanation:

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

your answer would be a. 12.5 kg