Here's why:

* Valence Electrons: These are the electrons in the outermost shell of an atom, which are involved in chemical bonding.

* Stability: Atoms strive to achieve a stable electron configuration, often resembling the nearest noble gas.

* Beryllium: Beryllium has an atomic number of 4, meaning it has 4 electrons. Its electron configuration is 1s² 2s². The 2s² represents its two valence electrons.

* Noble Gas Configuration: Helium (He), the nearest noble gas to beryllium, also has 2 electrons (1s²).

Therefore, beryllium's two valence electrons create a stable, noble gas-like configuration, making it relatively unreactive.