How Atoms Become Stable | Bohr Models and Valence Electrons

Added: 2026-05-20

[00:00:00]Atoms react because they're trying to become stable, and in chemistry, stable usually means a full outer energy level of electrons. The outer electrons are called valence electrons, and those are the electrons involved in reactions. If an atom already has a full outer shell, usually eight valence electrons, it's already stable, and that's why noble gases barely ever react. But most atoms don't have full outer shells, so they'll gain or lose electrons to get one. If an atom has one valence electron, it usually loses it because that leaves the level underneath full, so the atoms become stable and form a positive ion.

[00:00:31]If an atom has seven valence electrons, it usually gains one electron instead, and that fills the outer shell and forms a negative ion. What about two valence electrons? Well, they usually lose two.

[00:00:41]And six valence electrons? Well, they're usually going to gain two. And so atoms are constantly trying to get that full outer energy level, and whether they gain or lose electrons depends on which option gets them there easier.