Question

HEY GUYS! PLEASE ANSWER THIS!

Why is vanderwall's radius greater than metallic radius even when both are calculated in the same way?

I WILL MARK AS THE BRAINLIEST!

Answer 1

The van der Waals radius and the covalent radius actually deal with two different situations. The former is used when dealing with atoms that are not bonded, and the latter is used for atoms that are covalently bonded. ... Since a part of their electron clouds overlap, the atoms will be a little closer to each 

Answer 2

down vote

As Joseph's comment above alludes to, the 3d electrons in Gallium exhibit poor shielding, which causes a phenomenon known as "d-block contraction" as seen in elements from Ga to Br. Despite being in the same group as Aluminium, the introduction of the d-orbital means Ga has significantly more protons (31 vs 13) so the positively-charged nucleus has a much greater pull in Ga than in Al. Because of d-block contraction the nucleus is able to exert much greater pulling power on the outermost s- and p-level electrons thus reducing the atomic radius. This also cause the ionisation potential of Ga to be higher than that of Al, when the normal trend is for ionisation potential to decrease down a group.

you look at the Van der Waals radii of the elements, (more representative of a monoatomic gaseous atom) you will see that aluminum is actually smaller though not by a lot, giving some credence to the d-electrons explanations, but not a complete explanation in regard to the metallic radius.