* Lithium is an alkali metal, located in Group 1 of the periodic table. Alkali metals are highly reactive because they have only one valence electron (electron in the outermost shell) that they readily lose to form a +1 cation. This makes them eager to react with other elements to achieve a stable electron configuration.

* Neon is a noble gas, located in Group 18 of the periodic table. Noble gases have a full outer shell of electrons, making them very stable and unreactive. They rarely form compounds.

In summary:

* Lithium: Highly reactive due to its single valence electron.

* Neon: Very unreactive due to its full outer shell of electrons.