Question

Think of the reaction shown here as involving the transfer of a fluoride ion from \(\mathrm{ClF}_{3}\) to \(\mathrm{AsF}_{5}\) to form the ions \(\mathrm{ClF}_{2}^{+}\) and \(\mathrm{AsF}_{6}^{-}\). As a result, the hybridization scheme of each central atom must change. For each reactant molecule and product ion, indicate (a) its geometric structure and (b) the hybridization scheme for its central atom. $$ \mathrm{ClF}_{3}+\mathrm{AsF}_{5} \longrightarrow\left(\mathrm{ClF}_{2}^{+}\right)\left(\mathrm{AsF}_{6}^{-}\right) $$

Short answer

The geometric structure and hybridization scheme for each compound are as follows: ClF3 is T-shaped and SP3D, AsF5 is trigonal bipyramidal and SP3D, ClF2+ is linear and SP, AsF6- is octahedral and SP3D2.

Step-by-step solution

Determine Geometric Structure of ClF3

The central atom Cl has 7 valence electrons. ClF3 has 5 electron pairs around the central atom (2 lone pairs + 3 bonds with F). Thus, the shape is T-shaped due to 3 bonding pairs and 2 lone pairs of electrons.

Determine Hybridization of ClF3

The SP3D hybridization occurs when there are 5 electron pairs around the central atom, which matches with ClF3. So, the hybridization scheme of ClF3 is SP3D.

Determine Geometric Structure of AsF5

The central atom As has 5 valence electrons. AsF5 has 5 electron pairs around the central atom (all are bonding pairs with F). Thus, the shape is trigonal bipyramidal.

Determine Hybridization of AsF5

The SP3D hybridization occurs when there are 5 electron pairs around the central atom, which matches with AsF5. So, the hybridization scheme of AsF5 is SP3D.

Determine Geometric Structure of ClF2+

Chlorine now forms 2 bonds with F and has 3 lone pairs of electrons. The geometric structure of ClF2+ is linear.

Determine Hybridization of ClF2+

The SP hybridization occurs when there are 2 electron pairs. So, the hybridization scheme of ClF2+ is SP.

Determine Geometric Structure of AsF6-

Arsenic bonds with 6 F atoms and there are no lone pairs. Its geometric structure is octahedral.

Determine Hybridization of AsF6-

The SP3D2 hybridization occurs when there are 6 electron pairs. So, the hybridization scheme of AsF6- is SP3D2.

Key concepts

Geometric Structure

The geometric structure of a molecule gives us insights into how the atoms are arranged in space and what shape the molecule takes. This is determined by the number of bonding pairs and lone pairs around the central atom. For example, in ClF_3, chlorine has three bonds with fluorine and two lone pairs. Therefore, its geometric structure is T-shaped due to the influence of the lone pairs on spatial arrangement.

Moving on to AsF_5, arsenic forms five bonds with fluorine, with no lone pairs, resulting in a trigonal bipyramidal structure. Here, all the electron pairs are bonding pairs which directly affect the geometric shape of the molecule.

After the reaction, ClF_2⁺, consists of two bonding pairs and three lone pairs, creating a linear geometry. Finally, AsF_6^-, is bonded to six fluorine atoms and exhibits an octahedral geometry with no lone pairs affecting the distribution of atoms.

Electron Pairs

In molecules, electron pairs can either participate in bonding or exist as lone pairs. Their arrangement around a central atom influences the molecule's overall shape.

To illustrate this, consider ClF_3: it has a total of five electron pairs—three are bonding pairs with fluorine while two remain as lone pairs. The presence of lone pairs is crucial as they occupy space and repel bonding pairs, thus determining a T-shaped geometric structure.

On the other hand, AsF₅ only has bonding pairs, devoid of lone pairs, resulting in a streamlined trigonal bipyramidal shape. When ClF_2⁺ forms, it retains two bonding pairs and three lone pairs, showcasing how fewer bonds and increased lone pair influence compact its structure into a linear form. In AsF_6^-, six bonding pairs and no lone pairs configure into an even octahedral structure.

Bonding

Bonding refers to the connections formed between atoms through electron sharing or transfer, resulting in the formation of molecules. In ClF_3, each chlorine atom shares its electrons with three fluorine atoms, forming three covalent bonds. The nature and number of these bonds, along with lone pairs, influence the molecule's spatial arrangement.

In the case of AsF_5, arsenic links to five fluorines, yielding five covalent bonds that follow a trigonal bipyramidal distribution. When transforming during a reaction, such as in the creation of ClF_2⁺, some bonds are altered, leading to a new linear bonding formation with two fluorines. For AsF_6^-, an additional bond with a fluoride ion results in an octahedral shape, showcasing how bonding alterations can drastically impact molecular geometry.

Valence Electrons

Valence electrons are the electrons located in the outermost electron shell of an atom, playing a critical role in chemical bonding and the formation of molecules.

For instance, chlorine in ClF₃ has seven valence electrons, part of which forms covalent bonds with three fluorine atoms, while the rest exist as lone pairs. These valence electrons are key in determining the molecule's shape and bonding characteristics.

Arsenic in AsF₅ utilizes its five valence electrons to establish bonds with fluorine atoms, resulting in a trigonal bipyramidal structure. With ClF_2⁺, the change in electron configuration where chlorine shares electrons with only two fluorines highlights the dynamic nature of valence electrons in molecular transformation. Finally, in AsF_6^-, additional electrons participating in the bonding further emphasize the importance of valence electrons in forming stable, complete structures like the octahedral shape.