Question

What is covalent radii and metallic radii ?

Answer 1

this is your answer hope helps;)

Answer 2

The covalent radius, rcov, is a measure of the size of an atom that forms part of one covalent bond.It is usually measured either in picometres or angstroms , with 1 Å = 100 pm.In principle, the sum of the two covalent radii should equal the covalent bond length between two atoms, R = r + r.
Metallic radius is defined as one-half of the distance between the two adjacent metal ions in the metallic lattice. This radius depends on the nature of the atom as well as its environment—specifically, on the coordination number (CN), which in turn depends on the temperature and applied pressure.

Basically Covalent Radius is sum of Radius of two atoms forming Covalent bond
and Metallic Radius is sum of Radius of two atoms forming metallic bond