You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.

The Inheritance Cycle is a series of fantasy books written by Christopher Paolini.
Solution: The Inheritance Cycle is a tetralogy of young adult high fantasy novels written by American author Christopher Paolini.
Why? The output sentence elaborates on the input sentence without changing its general meaning e.g. "tetralogy of young adult high fantasy novels".

New input: The atomic radius of an element is the distance between the nucleus and the edge of the electron cloud .
Solution:
The atomic radius of a chemical element is a measure of the size of its atoms , usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons .