Question

1. an atom is most stable when it’s __________ (outer energy level) is filled with ____ electrons.

Explanation:

This question is about atomic stability in chemistry (a subfield of Natural Science). An atom's outermost energy level is called the valence shell. For most atoms (except hydrogen and helium in some cases), stability is achieved when the valence shell has 8 electrons (octet rule). The first blank refers to the "valence shell" (since the hint is outer energy level), and the second blank is 8 (or 2 for hydrogen/helium, but the octet rule is more general here).

Answer:

First blank: valence shell; Second blank: 8