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.