The elements that are largely unreactive substances are the noble gases. These include:

* Helium (He)

* Neon (Ne)

* Argon (Ar)

* Krypton (Kr)

* Xenon (Xe)

* Radon (Rn)

Here's why they are unreactive:

* Full outer electron shells: Noble gases have a complete outer shell of electrons. This stable configuration makes them very reluctant to gain or lose electrons, which is necessary for chemical bonding.

* High ionization energies: It takes a lot of energy to remove an electron from a noble gas atom, making them resistant to forming positive ions.

* Weak interatomic forces: Noble gases have very weak interatomic forces, which means they don't readily form bonds with other atoms.

While noble gases are generally unreactive, it's important to note that some heavier noble gases (like xenon) can form compounds under specific conditions. However, these reactions are still relatively rare and require special circumstances.