A young Danish scientist named (a)   studied the atom.

(a)   discovered that he could not point out exactly the electrons' path

The wave mechanical model depicts that electrons are moving in certain regions or areas around the atom called (a)  

This new model is a mathematical analysis and interpretation of both the particle and wave nature of the electrons. It is called the (a)   of the atom

The atom has specific energy levels which may be pictured like an inverted triangle, and electrons can be found within these energy levels. These levels are known as (a)   .

Each of these levels is further divided into what is called as (a)  

The (a)   sublevel has only one orbital

The (a)   sublevels has three orbitals

The 1s and consequently 2s sublevels are (a)   in shape