Question

How many valence electrons does helium have?

Answer 1

The electron distribution and the configuration giving us the value of valence electrons in the outermost shell.
Helium is the noble gas element but slightly different from other noble gas elements of the same group.

Complete step-by-step answer: Let us know about the element in detail;
Helium-
A noble gas element having atomic number as 2; residing in period 1 and group 18 of the modern periodic table. As the atomic number is two thus, only two electrons are present in the outermost shell.
The valence electrons are the electrons present in the last shell which can be equal to the valency of an element at times. In the case of helium, the outermost electrons are the valence electrons i.e. 2.
This can be properly shown by the electronic configuration of the same;
$He=1{{s}^{2}}$ ; these 2 electrons are the valence electrons having valency zero as its duplet is complete.
Due to its stability, it is being placed in the noble group of elements as it does not require any external electron to satisfy its state.

Note: Do note that the concept and definitions of valence electrons and valency is different; sometimes they are equal to each other but not always. So, do not get confused with these concepts.