Answer:
a. Chemical bonds.
Step-by-step explanation:
Hello,
In this case, it is necessary to know that when two elements are not stable by their own they should bond with an other atom of the same element via chemical bonds whereby the valence electrons act as bridges connecting the atoms. Some examples are diatomic-gaseous hydrogen, oxygen, nitrogen, chlorine, iodine, fluorine and bromine. Moreover, such chemical bonding is represented by lines binding the elements as shown on the attached picture.
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