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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 89

Although I3- is a known ion, F3- is not. (d) Yet another classmate says F3- does not exist because F is too small to make bonds to more than one atom. Is this classmate possibly correct?

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insert step 1> Consider the nature of the fluorine atom. Fluorine is the most electronegative element and typically forms only one bond due to its small size and high electronegativity.
insert step 2> Compare the size and bonding capabilities of fluorine with iodine. Iodine is much larger and can accommodate more atoms around it, which is why I3^- can exist.
insert step 3> Analyze the electron configuration of fluorine. Each fluorine atom has 7 valence electrons, needing only one more to complete its octet, which limits its ability to form multiple bonds.
insert step 4> Consider the steric and electronic factors. The small size of fluorine leads to high electron repulsion if more than one bond is attempted, making F3^- unlikely.
insert step 5> Conclude that the classmate's reasoning is plausible because the small size and high electronegativity of fluorine make it unlikely to form stable bonds with more than one other atom.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic and Covalent Bonding

Ionic bonding occurs when atoms transfer electrons, resulting in charged ions that attract each other. Covalent bonding involves the sharing of electrons between atoms. The ability of an atom to form multiple bonds depends on its size, electronegativity, and the number of available valence electrons.
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Atomic Size and Bonding Capacity

Atomic size influences an atom's ability to form bonds. Smaller atoms, like fluorine, have a high electronegativity and a limited number of valence electrons, which can restrict their ability to bond with multiple atoms. This is because the electron cloud is more concentrated, making it difficult to accommodate additional bonding partners.
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Stability of Polyatomic Ions

The stability of polyatomic ions, such as I3- and hypothetical F3-, depends on the arrangement of electrons and the overall charge. I3- is stable due to its ability to delocalize electrons, while F3- would likely be unstable because the small size of fluorine leads to high electron-electron repulsion, making it energetically unfavorable to bond with more than one atom.
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