The intramolecular bonds of octane and its electronegativity?

What are the intramolecular bonds in octane, and how can I provide some numerical data to prove it? I was thinking maybe I could calculate the electronegativity of octane to prove that it is non-polar covalent, but I'm not sure how to calculate the electronegativity of a molecule with so many different atoms bonded together (8 carbons and 18 hydrogens). Could someone please explain how to do this?