Chapter 8: Problem 89

Although \(\mathrm{I}_{3}\) is a known ion, \(\mathrm{F}_{3}^{-}\) is not. (a) Draw the Lewis structure for \(\mathrm{I}_{3}^{-}\) (it is linear, not a triangle). (b) One of your classmates says that \(\mathrm{F}_{3}^{-}\) does not exist because \(\mathrm{Fis}\) too electronegative to make bonds with another atom. Give an example that proves your classmate is wrong. (c) Another classmate says \(\mathrm{F}_{3}^{-}\) does not exist because it would violate the octet rule. Is this classmate possibly correct? (d) Yet another classmate says \(\mathrm{F}_{3}^{-}\) does not exist because \(\mathrm{F}\) is too small to make bonds to more than one atom. Is this classmate possibly correct?

Short Answer

Expert verified

The Lewis structure for \(I_{3}^{-}\) has a linear arrangement of three Iodine atoms, with three lone pairs on the central atom and two lone pairs on each outer atom. The non-existence of \(F_{3}^{-}\) is likely due to the violation of the octet rule and the small size of the Fluorine atom, making it difficult to bond with more than one atom. However, Fluorine's high electronegativity alone is not a sufficient reason, as it does form bonds in compounds like HF and PF6-.

Step by step solution

To draw the Lewis structure for I3-, first, arrange the three Iodine (I) atoms linearly because the question states that I3- is linear. Each Iodine atom has 7 valence electrons. Since the ion carries a negative charge, add one extra electron to the total, making it a total of 22 valence electrons to distribute. Place a single bond between the central atom and the two Iodine atoms on each side. Use the remaining electrons to complete the octets of all three Iodine atoms by placing lone pairs on them. This will give you three lone pairs on the central atom and two lone pairs on each outer atom. #Step 2: Discuss F3- ion existence or not using electronegativity#

One of the claims made by a classmate is that F3- ion does not exist because Fluorine (F) is too electronegative to make bonds with another atom. This is not entirely true, as Fluorine does form bonds with other atoms, often in the form of binary compounds like HF or in polyatomic anions such as PF6-. Thus, this claim cannot be the sole reason for the non-existence of F3- ion. #Step 3: Analyze F3- ion in terms of the octet rule#

Another classmate claims that F3- ion does not exist because it would violate the octet rule. If we attempt to draw a Lewis structure for F3-, we will find that Fluorine being the central atom, forms bonds with the other two Fluorine atoms. But, since each Fluorine atom already has 7 valence electrons and only needs one to complete its octet, it is impossible for the central Fluorine atom to form two bonds with two other Fluorine atoms without exceeding its octet. Therefore, this claim could be a valid reason for the non-existence of the F3- ion. #Step 4: Analyze F3- ion with respect to the size of Fluorine atom#

Another classmate claims that F3- ion does not exist because Fluorine is too small to make bonds with more than one atom. Small atoms like Fluorine, having high electron density in their outermost shell, may not be able to form multiple covalent bonds due to the repulsion between their negatively charged electron clouds (lone pairs). Thus, this claim can also be a possible factor contributing to the non-existence of F3- ion. In conclusion, the reasons for the non-existence of F3- ion could be the violation of the octet rule and the small size of the Fluorine atom which causes difficulty in bonding with more than one atom. The high electronegativity of Fluorine does not automatically disqualify it from forming bonds with other atoms, as evidenced by compounds such as HF and PF6-.