* Atomic Number and Electrons: The number of electrons in an atom is equal to its atomic number. An element with 86 electrons has an atomic number of 86.

* The Periodic Table: The element with atomic number 86 is Radon (Rn). Radon is a noble gas.

* Noble Gases: Noble gases are located in Group 18 of the periodic table. They have a full outer shell of electrons, making them incredibly stable and unreactive.

In summary: Elements with a full outer shell of electrons, like Radon, are considered inert because they don't readily form chemical bonds with other elements.