In this section, we will continue to look at more examples of covalent bonding between other elements.

Other elements that combine to form diatomic (two-atom) molecules, like hydrogen, are those in the halogen column. Their elements are fluorine, chlorine, bromine, iodine, and astatine. These elements have seven valence electrons (electrons in the outermost shell). The following diagram shows the outermost shell of fluorine and chlorine.

When two atoms of the same element overlap their half-empty p orbital, they form a covalent bond because each of the atom has achieved a stable octet. For example, look at the two fluorine atoms that bond to form a single fluorine molecule.


So far we discussed how two atoms of the same element can form diatomic molecules. But covalent bonding is not restricted to atoms of the same element. We will look at hydrogen chloride, which is a binary covalent compound. The following diagram shows a hydrogen and a chlorine atom before bonding.

When they bond, the half-empty 1s orbital of hydrogen shares its electron with the half-empty 3pz orbital of chlorine. Thus, they both achieve a stable octet; hydrogen achieves one of helium and chlorine that of argon. This diagram illustrates how the electron orbitals overlap.

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