The reason that Neon(Ne) is verty unreactive is because it's naturally occuring atomic structure allows it to satisfy the octet rule.The octet rule explains why many atoms form bonds. The octet rule states that all atoms try to achieve having 8 electrons in its outer-most shell so that it is full. Fulfilling the octet rule makes Neon a very stable compound and unlikely to bond like other elements do.
Other elements that naturally satisfy the octet rule are all of the "Noble Gasses" because the all have 8 valence(outer) electrons. Xenon(Xe) is another example of a noble gas.
The reason that the answers are NOT:
Sodium(Na)- has one valence electron that it wants to lose to have a filled outer ring. Therefore, Sodium usually loses an electron when it reacts to achieve a +1 charge. It does this by forming "ionic bonds" with negatively . charged non metals that usually have just 5-7 valence electrons and are looking to steal one from sodium because it is less energy for them to steal one electron than to get rid of all of theirs.
Boron(B)- has 3 valence electrons and usually reacts by sharing it electrons with other electron deficient non-metals in bonds called covalent bonds.
Phosphorus(P)- has 5 valence electrons and is tends to react with metallic atoms by stealing their valence electrons to obtain 3 more electrons.
