Question

while the maximum number of electrons required to fill the outermost shell of an atom varies depending on the size of the atom, almost all of the smaller atoms (atomic numbers 2-20) are considered stable, and thus nonreactive, when they contain ______ electron(s) in the outermost shell.

a) 8

b) 16

c) 1

d) 2

Explanation:

The octet rule states that for most small atoms (atomic numbers 2 - 20), a stable electron configuration in the outermost shell is achieved with 8 electrons (except for hydrogen and helium, but the question specifies atoms with atomic numbers 2 - 20, excluding the special case of helium's 2 electrons for stability in its context here). So the stable number of electrons in the outermost shell for these atoms is 8. Option A is correct as 16 is too many, 1 is reactive, and 2 is only stable for very small atoms like helium (not in the general 2 - 20 range here as per the octet rule application).

Answer:

A) 8