When constructing Lewis dot structures for molecules that are exceptions to the octet rule, how can adding an atom affect the arrangement of existing atoms or lone pairs?

• A. It always forces all atoms to achieve exactly eight electrons in their valence shell.
• B. It only affects the central atom and never the surrounding atoms or lone pairs.
• C. It has no effect on the positions of existing atoms or lone pairs.
• D. It may cause existing atoms or lone pairs to shift positions to minimize formal charges or accommodate expanded octets.

Answer: (D)

Verified step by step guidance

1. Understand that Lewis dot structures represent the arrangement of valence electrons around atoms in a molecule, aiming to satisfy the octet rule where possible.
2. Recognize that some molecules are exceptions to the octet rule, meaning atoms can have fewer or more than eight electrons in their valence shell.
3. When adding an atom to a Lewis structure, consider that the new atom can influence the distribution of electrons and bonding around the central atom and other atoms.
4. Realize that to minimize formal charges and achieve the most stable structure, existing atoms or lone pairs may need to shift positions, such as forming double or triple bonds or expanding the octet of the central atom.
5. Therefore, adding an atom can cause rearrangement of bonds and lone pairs to accommodate the new atom while maintaining the lowest possible formal charges and stable electron configurations.