Question

Explain what you understand by covalent radius, van der Waals radius,ionic radius and atomic radius. How do they vary in a period and in a group?

Answer 1

Covalent radius: Covalent bond radius refers to half of the distance two singly bonded atom of the same element. (Homonuclear $X-X$ bond)

Van der Waals Radius: It is defined as half of the internuclear separation of two non- bonded atoms of the same element on their closest possible approach.

Atomic radius: The distance from the center of the nucleus to the outermost shell containing electron.

Ionic radius: It is a radius of an atom's ion in ionic structure. It is denoted by $r_{ion}$.

The covalent and van der Waals radii decrease with increase in atomic number as we move from left to right in a period.

The atomic radius abruptly increases as we move from halogens to an inert gas.