Question

Suggest likely structures for (a) \(\left[\mathrm{F}_{2} \mathrm{ClO}_{2}\right]^{-},(\mathrm{b}) \mathrm{FBrO}_{3}\) (c) \(\left[\mathrm{ClO}_{2}\right]^{+},(\mathrm{d})\left[\mathrm{F}_{4} \mathrm{ClO}\right]^{-}\)

Short answer

(a) Cl central, (b) Br central, (c) Cl central, (d) Cl central.

Step-by-step solution

Understand the Problem

We are tasked to suggest the likely molecular structures for the given chemical species. Structures involve the arrangement of atoms and the bonds between them.

Analyze \\[\mathrm{F}_{2} \mathrm{ClO}_{2}]^{-}\\

Determine the valence electrons: F=7, Cl=7, O=6. The total is 2(F) + 1(Cl) + 2(O) + 1 (charge) = 2*7 + 7 + 2*6 + 1 = 34 electrons. A possible structure is where chlorine is the central atom, bonded to two fluorine atoms and two oxygen atoms with resonance possible between Cl-O bonds. One lone pair on chlorine accommodates the extra electron from the negative charge.

Analyze FBrO_{3}

Calculate the number of valence electrons: F=7, Br=7, O=6. The total is 7(F) + 7(Br) + 3*6(O) = 32 electrons. A probable structure is bromine as the central atom with a single F atom bonded to it, and each of the three O atoms double-bonded, forming typical oxybromine-like structures.

Analyze \\[\mathrm{ClO}_{2}]^{+}\\

Determine valence electrons: Cl=7, O=6. The total electrons are 7(Cl) + 2*6(O) - 1 (charge) = 18 electrons. A likely structure involves chlorine as the central atom double-bonded to two oxygens with a positive charge, suggesting a two-coordinated structure.

Analyze \\[\mathrm{F}_{4} \mathrm{ClO}]^{-}\\

Calculate valence electrons: F=7, Cl=7, O=6. Total is 4*7(F) + 7(Cl) + 6(O) + 1(charge) = 40 electrons. Chlorine is the central atom with four single bonds to F atoms and one double bond to O, similar in structure to perchlorate compounds, but with extra fluorine atoms surrounding chlorine.

Key concepts

Valence Electrons Calculation

The process of calculating valence electrons is crucial for predicting molecular structures. Valence electrons are the electrons in an atom's outermost shell. These play a key role in forming bonds with other atoms. To determine the number of valence electrons for a molecule, you sum up the valence electrons of all the atoms in the chemical species.

• Start by identifying the group number of each element in the periodic table. Elements in the same group usually have the same number of valence electrons. For example, both fluorine and chlorine, which belong to group 17, each have 7 valence electrons.
• For ions, adjust the total by adding an electron for negative charges and subtracting one for positive charges. This is critical for obtaining the correct electron count unique to that species.

Let's illustrate this with an example: in \([\mathrm{F}_{2} \mathrm{ClO}_{2}]^{-}\), the total valence electrons calculation would be: 2 fluorine atoms (each with 7) + 1 chlorine atom (7) + 2 oxygen atoms (each with 6) + 1 extra electron from the charge. This sums up to a total of 34 valence electrons. Understanding these calculations helps in accurately predicting how atoms will bond in a molecule, influencing the molecular shape and structure.

Resonance Structures

Some molecules can be represented by two or more valid Lewis structures. These structures are called resonance structures. It's important to note that no single resonance structure accurately represents the molecule. Instead, the actual structure is a hybrid of all possible resonance structures. This phenomenon occurs due to the delocalization of electrons across different bonds. In your studies, you may encounter molecules such as \([\mathrm{F}_{2} \mathrm{ClO}_{2}]^{-}\) where resonance is relevant. Here, the chlorine can form different bonding configurations with oxygen: either single or double bonds. The true configuration would be a resonance hybrid of these states, illustrating the flexibility within the oxygen-chlorine bonds.The benefit of resonance is its ability to account for the experimentally observed properties of molecules that a single Lewis structure cannot. It also explains certain properties such as stability and reactivity that are characteristic of molecules like aromatic compounds. Recognizing resonance structures expands understanding of how molecules might exist in a more stable and energetically favorable form.

Central Atom Identification

Identifying the central atom in a molecule is crucial for predicting its geometry. Typically, the central atom is the least electronegative atom, often capable of forming multiple bonds. This element serves as the backbone to which others attach.When constructing molecular structures, start by considering the atom with the highest valence capacity or that most conventionally serves as a central atom, such as carbon in most organic compounds or chlorine in \([\mathrm{F}_{2} \mathrm{ClO}_{2}]^{-}\).

• The central atom usually can form enough bonds to accommodate surrounding atoms. For example, in \([\mathrm{F}_{2} \mathrm{ClO}_{2}]^{-}\), chlorine acts as the central atom and is bonded to two fluorines and two oxygens.
• Considerations include atomic size and the presence of lone pairs, which can dictate bond angles and lengths.

Having a clear methodology to determine the central atom enables the construction of more accurate molecular models, allowing predictions for physical and chemical properties of the compound.