What do you mean by covalent radius?

How do atomic radius vary in a period and in a group? How do you explain the variation?

Why do the noble gas elements have exceptionally high atomic radii?
Or
In a period, generally the size of the atom decreases with rise in atomic number, but at the end of each period, atomic size of the noble gas increases abruptly. Why is it so?

Atomic radii of noble gases are essentially the vander Waal's radii. Comment.

What is ionic radius?

Why is the radius of cation less than that of parent atom?

Why is the radius of anion more than that of the parent atom?

What does atomic radius and ionic radius really mean to you?