Chapter 15: Problem 62
Use Lewis symbols to diagram the reaction $$ \mathrm{BF}_{3}+\mathrm{F}^{-} \longrightarrow \mathrm{BF}_{4} $$
Short Answer
Expert verified
In the reaction, BF3 accepts an electron pair from F- to form BF4-, which satisfies the octet rule for all atoms.
Step by step solution
01
Determine the Valence Electrons for Boron (B)
Boron (B) is in Group 13 of the periodic table and has three valence electrons. Its Lewis symbol is a B with three dots around it, representing the three valence electrons.
02
Determine the Valence Electrons for Fluorine (F)
Fluorine (F) is in Group 17 of the periodic table and has seven valence electrons. Its Lewis symbol is an F with seven dots around it: one single lone pair and five unpaired electrons.
03
Draw the Lewis Structure for BF3
For BF3, boron is the central atom with three fluorine atoms around it. Each bond between boron and a fluorine atom is represented by a pair of dots (or a line representing two electrons) between the B and each F. After forming three single bonds, boron lacks an octet but each fluorine has an octet.
04
Represent the Fluoride Ion (F-)
The fluoride ion has an extra electron compared to a neutral fluorine atom, giving it a total of eight valence electrons. Its Lewis symbol is an F surrounded by eight dots and a negative sign indicating the extra electron.
05
Combine BF3 and F- to Form BF4-
The fluoride ion can donate its extra electron pair to the boron atom in BF3 to achieve a stable octet for boron. Place the F- near the BF3 so that its extra pair of electrons (the lone pair) forms a bond with boron, giving a final structure where boron is in the center with four fluoride ions around it, and boron now has an octet.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Valence Electrons
Valence electrons are pivotal in understanding how elements interact and bond with each other. They are the electrons located in the outermost shell of an atom and are responsible for an atom's chemical properties.
In the exercise, boron (B) has three valence electrons, and fluorine (F) has seven. When it comes to drawing Lewis structures, these electrons are represented as dots surrounding the chemical symbol. A careful count of an element's position in the periodic table can help us determine how many valence electrons it has. For example, elements in Group 13, like boron, have three valence electrons, whereas those in Group 17, like fluorine, have seven.
It is these electrons' ability to form bonds by either sharing, losing, or gaining electrons that drives chemical reactions forward. The exercise demonstrates how to use the Lewis symbol to represent these valence electrons for individual atoms before they form compounds.
In the exercise, boron (B) has three valence electrons, and fluorine (F) has seven. When it comes to drawing Lewis structures, these electrons are represented as dots surrounding the chemical symbol. A careful count of an element's position in the periodic table can help us determine how many valence electrons it has. For example, elements in Group 13, like boron, have three valence electrons, whereas those in Group 17, like fluorine, have seven.
It is these electrons' ability to form bonds by either sharing, losing, or gaining electrons that drives chemical reactions forward. The exercise demonstrates how to use the Lewis symbol to represent these valence electrons for individual atoms before they form compounds.
Octet Rule
The octet rule is a key foundational concept in chemistry that guides us in predicting the chemical bonding behavior of atoms. It posits that atoms tend to bond in such a way that they each end up with eight electrons in their valence shell, giving them the same electronic configuration as a noble gas.
Boron, in our exercise, is an exception to the octet rule as it is satisfied with having six electrons in its valence shell when bonded in \textbf{BF}\(_3\). The fluorine atoms follow the octet rule strictly, each having eight electrons after forming single bonds with boron. However, when \textbf{BF}\(_3\) reacts with a fluoride ion (\textbf{F}\(^-\)), boron achieves a full octet by accepting a pair of electrons from the fluoride ion, resulting in the formation of \textbf{BF}\(_4^-\).
Understanding the octet rule helps in predicting the stability of compounds and the formation of ions, as seen with the fluoride ion, which has eight valence electrons, indicating full stability as per the octet rule.
Boron, in our exercise, is an exception to the octet rule as it is satisfied with having six electrons in its valence shell when bonded in \textbf{BF}\(_3\). The fluorine atoms follow the octet rule strictly, each having eight electrons after forming single bonds with boron. However, when \textbf{BF}\(_3\) reacts with a fluoride ion (\textbf{F}\(^-\)), boron achieves a full octet by accepting a pair of electrons from the fluoride ion, resulting in the formation of \textbf{BF}\(_4^-\).
Understanding the octet rule helps in predicting the stability of compounds and the formation of ions, as seen with the fluoride ion, which has eight valence electrons, indicating full stability as per the octet rule.
Chemical Bonding
Chemical bonding is the force that holds atoms together in a compound. Atoms form chemical bonds to achieve stability, usually by filling their outer electron shell according to the octet rule. There are a few types of bonds, primarily ionic, covalent, and metallic bonds.
In the given exercise, the bonding is covalent, as atoms share electrons to achieve stability. Initially, boron shares one electron with each of the three fluorine atoms in \textbf{BF}\(_3\), resulting in three covalent bonds. When the fluoride ion, which has an extra electron, comes into play, it shares its lone pair of electrons with the boron atom, forming a new covalent bond and resulting in \textbf{BF}\(_4^-\).
This sharing of electrons is the heart of covalent bonding and is beautifully illustrated in the step-by-step construction of the Lewis structure in the exercise. The tendency of boron to form compounds where it does not have a complete octet, and the way it obtains it through reaction with a fluoride ion is a prime example of the flexibility within chemical bonding concepts.
In the given exercise, the bonding is covalent, as atoms share electrons to achieve stability. Initially, boron shares one electron with each of the three fluorine atoms in \textbf{BF}\(_3\), resulting in three covalent bonds. When the fluoride ion, which has an extra electron, comes into play, it shares its lone pair of electrons with the boron atom, forming a new covalent bond and resulting in \textbf{BF}\(_4^-\).
This sharing of electrons is the heart of covalent bonding and is beautifully illustrated in the step-by-step construction of the Lewis structure in the exercise. The tendency of boron to form compounds where it does not have a complete octet, and the way it obtains it through reaction with a fluoride ion is a prime example of the flexibility within chemical bonding concepts.
