Why do atoms share electrons in covalent bonds?

to become more polar

to become ions and attract each other

to attain a noble-gas electron configuration

to increase their atomic numbers

The correct option is "to attain a noble-gas electron configuration"

Explanation:

All elements (with the exception of the noble gases) in the periodic table wants to achieve there duplet or octet configuration; they want there outermost shell to be completely filled (like the noble gases).

Atoms of these elements do this in different ways during chemical combinations. For instance, during electrovalent combination, some atoms donate electron(s) (so as to have a completely filled outermost shell) and some receive electron(s) (for the same reason of having a completely filled outermost shell).

During covalent combinations also, atoms share electrons on there outermost shell so they (the atoms involved) can have a completely filled outermost shell and hence attain a noble-gas electron configuration.

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements