Question

5. Noble gases, the elements in group 18 of the periodic table, do not react easily with other elements. Explain why you think they are not very reactive.

Answer 1

chemical properties of elements depend on their electron configuration. If an elements electrons are occupying fully all orbitals, minimal energy is attained and thus highest chemical stability. Remember chemical bond theories, ionic bond, and covalent bonds, those are just ways for elements to attain higher stability (they bind with other elements to achieve the energetically most favourable order of electrons).
Noble gases have their orbitals full of electrons, and are hard to modify, hence, stable.
in practice noble gases can bind to a few other elements, but those are exceptions.

Answer 2

they have 8 valence electrons

Answer 3

The noble gases are relatively nonreactive. This is because they have a complete valence shell (or complete Octet, meaning stable configuration) They have little tendency to gain or lose electrons. The noble gases have high ionization energies and negligible electronegativities