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

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

Explanation:

Mosely revised the periodic table trend devised by Mendelev by changing the criterion of atomic mass to atomic number.

The atomic number defines the atomic radius as well as ionization energy trends in the periodic table. The atomic number or the number of positively charged protons determines the atomic radius. With increase in positive charge, the atomic radius decreases due to electron proximity towards the nucleus.

In a periodic table:

Across a period - nuclear charge increases, a greater attraction between the valence shell electron and nucleus

Down a group - nuclear charge increases, shielding increases due to more electron shells, a lesser attraction between the valence shell electron and nucleus. Based on this,

Across a period - atomic radius decreases and first ionization energy increases

Down a group - atomic radius increases and 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:

Both these trends were well explained and supported by genuine reasons. As we go down a group in periodic table, a new shell is added at each level, which increases the size and hence the radius of the atom and the size of atom increases which means the outermost shell is increasingly moving farther from the atom. Due to this fact, electrons experience less attractive force from the nucleus and electrons are easily removed, so the first ionization energy decreases.