Write Lewis structures that obey the octet rule for each of the following molecules and ions. (In each case the first atom listed is the central atom.) a. $\mathrm{POCl}_{3}, \mathrm{SO}_{4}^{2-}, \mathrm{XeO}_{4}, \mathrm{PO}_{4}^{3-}, \mathrm{ClO}_{4}^{-}$ b. $\mathrm{NF}_{3}, \mathrm{SO}_{3}^{2-}, \mathrm{PO}_{3}^{3-}, \mathrm{ClO}_{3}^{-}$ c. \(\mathrm{ClO}_{2}-, \mathrm{SCl}_{2}, \mathrm{PCl}_{2}^{-}\) d. Considering your answers to parts a, b, and c, what conclusions can you draw concerning the structures of species containing the same number of atoms and the same number of valence electrons?

1. First, count the total number of valence electrons for each molecule or ion. 2. Place the least electronegative atom as the central atom. 3. Draw single bonds between the central atom and surrounding atoms. 4. Distribute the remaining electrons to satisfy the octet rule for all atoms. The Lewis structures for each molecule or ion are as follows: \(\mathrm{POCl}_{3}\): \[ \chemfig{P(-[:0]O)(-[:-90]Cl)(-[:90]Cl)(-[:180]Cl)} \] \(\mathrm{SO}_{4}^{2-}\): \[ \chemfig{S(=[:0]O)(=[:90]O)(=[:180]O)(=[:-90]O)}^{-2} \] \(\mathrm{XeO}_{4}\): \[ \chemfig{Xe(=[:0]O)(=[:90]O)(=[:180]O)(=[:-90]O)} \] \(\mathrm{PO}_{4}^{3-}\): \[ \chemfig{P(-[:0]O)(-[:90]O)(-[:180]O)(-[:-90]O)}^{3-} \] \(\mathrm{ClO}_{4}^{-}\): \[ \chemfig{Cl(-[:0]O)(-[:90]O)(-[:180]O)(-[:-90]O)}^{-} \]

Follow the same procedure as mentioned earlier for each molecule or ion: \(\mathrm{NF}_{3}\): \[ \chemfig{N(-[1]F)(-[3]F)(-[5]F)} \] \(\mathrm{SO}_{3}^{2-}\): \[ \chemfig{S(-[:0]O)(-[:120]O)(-[:-120]O)}^{2-} \] \(\mathrm{PO}_{3}^{3-}\): \[ \chemfig{P(-[:0]O)(-[:90]O)(-[:-90]O)}^{3-} \] \(\mathrm{ClO}_{3}^{-}\): \[ \chemfig{Cl(-[:0]O)(-[:90]O)(-[:-90]O)}^{-} \]

Follow the same procedure as mentioned earlier for each molecule or ion: \(\mathrm{ClO}_{2}^{-}\): \[ \chemfig{Cl(=[:0]O)(-[:-90]O)}^{-} \] \(\mathrm{SCl}_{2}\): \[ \chemfig{S(-[:0]Cl)(-[:-90]Cl)} \] \(\mathrm{PCl}_{2}^{-}\): \[ \chemfig{P(-[:0]Cl)(-[:-90]Cl)}^{-} \]

From the Lewis structures of species containing the same number of atoms and valence electrons, we can draw the following conclusions: 1. The shape of the molecules or ions depends on the arrangement of atoms and electron pairs around the central atom. 2. Species with the same number of atoms and valence electrons might not necessarily have the same shape. 3. Species with different central atoms, even though they might have the same number of atoms and valence electrons, will have different arrangements of electrons due to differences in electronegativity and the central atom's ability to expand its valence shell.