Question

Covalent bonds tend to make atoms more stable by helping them

fill up their innermost electron shell.
fill up their outermost electron shell.
empty out their innermost electron shell.
empty out their outermost electron shell.

Answer 1

fill up their outermost electron shell.

Covalent bonds form when atoms share valence electrons so each atom attains a fuller (often noble gas–like) outer electron shell, increasing stability.