In atoms with only one shell how many electrons are requires for stability?

In general, atoms are most stable, least reactive, when their outermost electron shell is full. Most of the elements important in biology need eight electrons in their outermost shell in order to be stable, and this rule of thumb is known as the octet rule.

Explanation:

close lines strong magnet less close weaker

grav forces affect all objects magnetic forces affect magnetic objects and electric currents