Question

Question #669dc

Answer 1

Noble gases have a an octet configuration in which they are stable. Due to this they are generally inactive chemically although there are rare exceptions like `XeF_4`.

Explanation:

So they don't like to gain electrons (which would make them have an electronic configuration of group 1 elements which are highly reactive). Additionally, adding an electron would add a higher energy level to the atom, making it very unstable. So to force an electron to join an atom, a lot of energy must be expended (and put "into" the atom), and thus a positive enthalpy.

Think of it like this: if you compress a spring, you are giving it high potential energy because the spring really doesn't like to be so squished. Thus, the spring gains energy because it is forced into a higher energy state. The same is for the noble gases: when you force an electron in, it forces the noble gas to be at a higher (and more unstable) energy level.