How many valence electrons are there in an atom with the electron configuration [noble gas]ns2(n –1)d10np3?

There are 5 valence electrons in Valence Shell.

Example,
Lets take example of Arsenic with Atomic Number 33.
Its electronic Configuration is,
                      
                                                  [Ar]  4s², 3d¹⁰ 4p³

As the valence shell number is 4, so all the electrons present in shell 4 are said to be valence shell electrons and they are 5 in number.

The correct answer should be "electrons orbit the nucleus in circular motions exactly as shown on the classic bohr model."