Final answer:
Step 4 in writing Lewis structures with the Octet Rule is ensuring all atoms except hydrogen have an octet of electrons, which may involve forming double or triple bonds if necessary.
Step-by-step explanation:
Step 4 of writing Lewis structures with the Octet Rule involves checking that the octet of each atom is complete, with the exceptions of hydrogen, which follows a duet rule. If all atoms satisfy the octet rule, then the Lewis structure is considered complete. In cases where an atom does not have a complete octet, shared electron pairs (i.e., bonds) may be adjusted by forming double or triple bonds, ensuring that each element (except hydrogen) ends up with eight electrons, thus obeying the octet rule.
This step is critical for constructing proper Lewis structures, such as those for CH4 and PCl3. For molecules where the octet cannot be satisfied by single bonds alone, such as CO2 or HCN, multiple bonds are necessary. This step may require rearranging lone pairs of electrons to form double or triple bonds, thereby achieving a complete octet for each atom.