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Chapter 8: Problem 49

Which one of these statements about formal charge is true? (a) Formal charge is the same as oxidation number. (b) To draw the best Lewis structure, you should minimize formal charge. (c) Formal charge takes into account the different electronegativities of the atoms in a molecule. (d) Formal charge is most useful for ionic compounds. (e) Formal charge is used in calculating the dipole moment of a diatomic molecule.

Short Answer

Expert verified
The correct statement about formal charge is: (b) To draw the best Lewis structure, you should minimize formal charge.

Step by step solution

01

(a) Formal charge is the same as oxidation number

Formal charge and oxidation numbers are different concepts in chemistry. Formal charge represents the charge an atom would have if the bonding electrons were shared equally, while oxidation number indicates the number of electrons an atom has theoretically gained or lost. Thus, statement (a) is incorrect.
02

(b) To draw the best Lewis structure, you should minimize formal charge

When drawing a Lewis structure, it is important to minimize the formal charges on each atom, as a structure with low or zero formal charges would be more stable. The most stable Lewis structures will generally result in a molecule or ion with the lowest possible formal charges on the individual atoms. Therefore, statement (b) is correct.
03

(c) Formal charge takes into account the different electronegativities of the atoms in a molecule

The concept of formal charge assumes that electrons in a covalent bond are shared equally between the bonded atoms, regardless of their electronegativity. Electronegativity is better represented through other concepts, such as bond polarity and dipole moments. Therefore, statement (c) is incorrect.
04

(d) Formal charge is most useful for ionic compounds

The concept of formal charge is more commonly used to evaluate covalent compounds' stability, rather than ionic compounds. In ionic compounds, the charge on each ion is more clearly defined, and the concept of oxidation number is more relevant. Therefore, statement (d) is incorrect.
05

(e) Formal charge is used in calculating the dipole moment of a diatomic molecule

The dipole moment of a molecule arises from the difference in electronegativities between the atoms involved and the distance between them. Formal charge does not take electronegativities into account and is not directly involved in calculating the dipole moment. Thus, statement (e) is incorrect. Based on the analysis, the correct answer is: (b) To draw the best Lewis structure, you should minimize formal charge.

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Most popular questions from this chapter

Predict the chemical formula of the ionic compound formed between the following pairs of elements: (a) Al and F, (b) K and \(S,(\mathbf{c}) \mathrm{Y}\) and \(\mathrm{O},(\mathbf{d}) \mathrm{Mg}\) and \(\mathrm{N} .\)

A common form of elemental phosphorus is the tetrahedral \(\mathrm{P}_{4}\) molecule, where all four phosphorus atoms are equivalent: At room temperature phosphorus is a solid. (a) Are there any lone pairs of electrons in the \(\mathrm{P}_{4}\) molecule? (b) How many \(\mathrm{p}-\mathrm{p}\) bonds are there in the molecule? (c) Draw a Lewis structure for a linear \(P_{4}\) molecule that satisfies the octet rule. Does this molecule have resonance structures? (d) On the basis of formal charges, which is more stable, the linear molecule or the tetrahedral molecule?

By referring only to the periodic table, select (a) the most electronegative element in group \(6 \mathrm{A} ;(\mathbf{b})\) the least electronegative element in the group Al, Si, P; (c) the most electronegative element in the group \(\mathrm{Ga}, \mathrm{P}, \mathrm{Cl}, \mathrm{Na} ;(\mathbf{d})\) the element in the group \(\mathrm{K}\) \(\mathrm{C}, \mathrm{Zn}, \mathrm{F}\) that is most likely to form an ionic compound with Ba.

Energy is required to remove two electrons from Ca to form \(\mathrm{Ca}^{2+},\) and energy is required to add two electrons to \(\mathrm{O}\) to form \(\mathrm{O}^{2-} .\) Yet \(\mathrm{CaO}\) is stable relative to the free elements. Which statement is the best explanation? (a) The lattice energy of CaO is large enough to overcome these processes. (b) CaO is a covalent compound, and these processes are irrelevant. (c) CaO has a higher molar mass than either Ca or O. (d) The enthalpy of formation of CaO is small. (e) CaO is stable to atmospheric conditions.

(a) Describe the molecule xenon trioxide, \(\mathrm{XeO}_{3},\) using four possible Lewis structures, one each with zero, one, two, or three \(\mathrm{Xe}-\mathrm{O}\) double bonds. (b) Do any of these resonance structures satisfy the octet rule for every atom in the molecule? (c) Do any of the four Lewis structures have multiple resonance structures? If so, how many resonance structures do you find? (d) Which of the Lewis structures in part (a) yields the most favorable formal charges for the molecule?
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