what is the differencebetween metallic radius and ionic radius? hw do we measure each

atomic radii is the radius of the atom when it's in neutral.

ionic radii is the radius of the atom when it losses or gains electron ( become an ion)

so for the very same element the number of electrons in atom differs than the number of electrons of the ion which might cause a change in the number of orbitals and the radius.

As an example:

Oxygen loves to accept two electrons to make a perfect octete or "8" electron valence shell of electrons. This ion with it's 2 extra electrons has a radius of: 1 .40 A

Without the two added electrons, it has a radius of: 66 pm

Sometimes the atomic radius is larger, sometimes it is smaller than the neutral atom

hope this helps