Chapter 7

Draw electron-dot structures for the following molecules: (a) \(\mathrm{H}_{2}\) S, hydrogen sulfide, a poisonous gas produced by rotten eggs (b) \(\mathrm{CHCl}_{3}\), chloroform, an anesthetic

Use the octet rule to predict the molecular formula of compounds that form between the elements (a) oxygen and fluorine. (b) silicon and chlorine.

Identify the correct electron-dot structure for \(\mathrm{POCl}_{3} .\) Explain what is wrong with the incorrect ones.

Draw an electron-dot structure for the following molecules or ions: (a) \(\mathrm{CO}\) (b) \(\mathrm{HCN}\) (c) \(\mathrm{CO}_{3}^{2-}\) (d) \(\mathrm{CO}_{2}\)

Identify the correct electron-dot structure(s) for phosphate, \(\mathrm{PO}_{4}{\underline{\phantom{xx}}}^{3-}\). Explain what is wrong with the incorrect ones. Is it reasonable to have more than one correct electrondot structure? Explain.

Draw an electron-dot structure for the following radicals: (a) \(\mathrm{ClO}_{2}\) (involved in depletion of stratospheric ozone) (b) Hydroxyl, OH (important in atmospheric chemistry, aging, and the development of disease) (c) Ethyl, \(\mathrm{C}_{2} \mathrm{H}_{5}\) (involved in synthesis of polyethylene polymer)

Which oxygen species do you predict to be most reactive? \(\mathrm{O}_{3}, \mathrm{O}_{2}, \mathrm{O}_{2}^{-} .\)

Draw an electron-dot structure for the following molecules or ions: (a) Methylamine, \(\mathrm{CH}_{5} \mathrm{~N}\) (b) Ethylene, \(\mathrm{C}_{2} \mathrm{H}\) (c) Propane, \(\mathrm{C}_{3} \mathrm{H}_{8}\) (d) Hydrogen Peroxide, \(\mathrm{H}_{2} \mathrm{O}_{2}\) (e) Hydrazine, \(\mathrm{N}_{2} \mathrm{H}_{4}\)

There are two molecules with the formula \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O} .\) Draw electron-dot structures for both. (Hint: The connection of atoms is different in the two structures.)

Called "laughing gas," nitrous oxide \(\left(\mathrm{N}_{2} \mathrm{O}\right)\) is sometimes used by dentists as an anesthetic. (a) Given the connections \(\mathrm{N}-\mathrm{N}-\mathrm{O}\) draw an electron- dot structure.

Draw as many resonance structures as possible for each of the following molecules or ions, giving all atoms (except H) octets. Used curved arrows to show how one structure can be converted into another. (a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{CO}_{3}^{2-}\) (c) \(\mathrm{BF}_{3}\)

Calculate the formal charge on each atom in the following electron-dot structures: (a) Cyanate ion: \([\ddot{\mathrm{N}}=\mathrm{C}=\ddot{\mathrm{O}}]^{-}\) (b) Ozone: \(: \ddot{\mathrm{O}}-\ddot{\mathrm{O}}=\ddot{\mathrm{O}}\)

Calculate formal charges on the \(\mathrm{C}\) and \(\mathrm{O}\) atoms in two resonance structures for acetic acid, the main component of vinegar. Decide which structure makes a larger contribution to the resonance hybrid.

In organophosphate compounds, phosphorus has an expanded octet. Why can phosphorus accommodate more than eight electrons in its electron-dot structure?

Draw the new electron-dot structures indicated by the curved arrows in the Sarin molecule. Decide if the new structure is valid and if so, calculate formal charges on \(\mathrm{F}, \mathrm{P}\), and both oxygen atoms. Compare formal charges to those calculated in Problem 7.27. Use formal charge to evaluate which structure is the major contributor to the resonance hybrid.

Match the following descriptions with the type of bond (ionic, nonpolar covalent, covalent). (a) One or more electrons are transferred from a metal to a non- metal atom. (b) Electrons are shared equally between two atoms. (c) Electrons are shared unequally by two atoms.

Why do two atoms come together to form a covalent bond? (a) Attractive forces between the positively charged nuclei and the electrons in both atoms occur when the atoms are close together. (b) Repulsive forces between protons in the nuclei of the two atoms are minimized when the atoms are close together. (c) Repulsive forces between electrons in the two atoms are minimized when the atoms are close together.

What general trends in electronegativity occur in the periodic table?

Order the following elements according to increasing electronegativity: \(\mathrm{Li}, \mathrm{Br}, \mathrm{Pb}, \mathrm{K}, \mathrm{Mg}, \mathrm{C}\).

Order the following elements according to decreasing electronegativity: \(\mathrm{C}, \mathrm{Ca}, \mathrm{Cs}, \mathrm{Cl}, \mathrm{Cu}\).

Which of the following substances are largely ionic, and which are covalent? (a) HF (b) HI (c) \(\mathrm{PdCl}_{2}\) (d) \(\mathrm{BBr}_{3}\) (e) \(\mathrm{NaOH}\) (f) \(\mathrm{CH}_{3} \mathrm{Li}\)

Which of the substances \(\mathrm{CdBr}_{2}, \mathrm{P}_{4}, \mathrm{BrF}_{3}, \mathrm{MgO}, \mathrm{NF}_{3}, \mathrm{BaCl}_{2}\) \(\mathrm{POCl}_{3}\), and LiBr are: (a) largely ionic? (b) nonpolar covalent? (c) polar covalent?

Which of the substances \(\mathrm{S}_{8}, \mathrm{CaCl}_{2}, \mathrm{SOCl}_{2}, \mathrm{NaF}, \mathrm{CBr}_{4}, \mathrm{BrCl}, \mathrm{LiF}\) and \(\mathrm{AsH}_{3}\) are: (a) largely ionic? (b) nonpolar covalent? (c) polar covalent?

Order the following compounds according to the increasing ionic character of their bonds: \(\mathrm{CCl}_{4}, \mathrm{BaCl}_{2}, \mathrm{TiCl}_{3}, \mathrm{ClO}_{2} .\)

Order the following compounds according to the increasing ionic character of their bonds: \(\mathrm{NH}_{3}, \mathrm{NCl}_{3}, \mathrm{Na}_{3} \mathrm{~N}, \mathrm{NO}_{2}\)

Using only the elements \(\mathrm{P}, \mathrm{Br}\), and \(\mathrm{Mg}\), give formulas for the following: (a) an ionic compound (b) a molecular compound with polar covalent bonds that obeys the octet rule and has no formal charges

Using only the elements Ca, Cl, Si, give formulas for the following: (a) an ionic compound (b) a molecular compound with polar covalent bonds that obeys the octet rule and has no formal charges

Which compound do you expect to have the stronger \(\mathrm{N}-\mathrm{N}\) bond, \(\mathrm{N}_{2} \mathrm{H}_{2}\) or \(\mathrm{N}_{2} \mathrm{H}_{4} ?\) Explain.

Which compound do you expect to have the stronger \(\mathrm{N}-\mathrm{O}\) bond, \(\mathrm{NO}\) or \(\mathrm{NO}_{2} ?\) Explain.

Explain the difference in the bond dissociation energies for the following bonds: \((\mathrm{C}-\mathrm{F}, 450 \mathrm{~kJ} / \mathrm{mol}),(\mathrm{N}-\mathrm{F}, 270 \mathrm{~kJ} / \mathrm{mol})\), \((\mathrm{O}-\mathrm{F}, 180 \mathrm{~kJ} / \mathrm{mol}),(\mathrm{F}-\mathrm{F}, 159 \mathrm{~kJ} / \mathrm{mol})\)

Explain the difference in the bond dissociation energies for the following bonds: \((\mathrm{C}-\mathrm{F}, 450 \mathrm{~kJ} / \mathrm{mol}),(\mathrm{C}-\mathrm{Cl}, 330 \mathrm{~kJ} / \mathrm{mol})\), \((\mathrm{C}-\mathrm{Br}, 270 \mathrm{~kJ} / \mathrm{mol}),(\mathrm{C}-\mathrm{I}, 240 \mathrm{~kJ} / \mathrm{mol})\)

Predict which of the following bonds should be strongest: \(\mathrm{N}-\mathrm{H}, \mathrm{O}-\mathrm{H}, \mathrm{S}-\mathrm{H}\)

Predict which of the following bonds should be weakest: \(\mathrm{Cl}-\mathrm{Cl}, \mathrm{Br}-\mathrm{Br}, \mathrm{I}-\mathrm{I}\)

Name the following molecular compounds: (a) \(\mathrm{PCl}_{3}\) (b) \(\mathrm{N}_{2} \mathrm{O}_{3}\) (c) \(\mathrm{P}_{4} \mathrm{O}_{7}\) (d) \(\mathrm{BrF}_{3}\) (e) \(\mathrm{NCl}_{3}\) (f) \(\mathrm{P}_{4} \mathrm{O}_{6}\) (g) \(\mathrm{S}_{2} \mathrm{~F}_{2}\) (h) \(\mathrm{SeO}_{2}\)

Write formulas for the following molecular compounds: (a) Disulfur dichloride (b) Iodine monochloride (c) Nitrogen triiodide (d) Dichlorine monoxide (e) Chlorine trioxide (f) Tetrasulfur tetranitride

Which of the following is most likely to be a gas at room temperature \(\left(25^{\circ} \mathrm{C}\right) ?\) (a) \(\mathrm{NH}_{3}\) (b) \(\mathrm{K}_{3} \mathrm{~N}\) (c) \(\mathrm{Ca}_{3} \mathrm{~N}_{2}\)

Which of the following is most likely to be a solid at room temperature \(\left(25^{\circ} \mathrm{C}\right) ?\) (a) \(\mathrm{H}_{2} \mathrm{~S}\) (b) \(\mathrm{SO}_{2}\) (c) \(\mathrm{Na}_{2} \mathrm{~S}\)

Why does the octet rule apply primarily to main-group elements, not to transition metals?

Which of the following substances contains an atom that does not follow the octet rule? (a) \(\mathrm{AlCl}_{3}\) (b) \(\mathrm{PCl}_{3}\) (c) \(\mathrm{PCl}_{5}\) (d) \(\mathrm{SiCl}_{4}\)

Draw electron-dot structures for the following molecules or ions: (a) \(\mathrm{CBr}_{4}\) (b) \(\mathrm{NCl}_{3}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}\) (d) \(\mathrm{BF}_{4}^{-}\) (e) \(\mathrm{O}_{2}^{2-}\) (f) \(\mathrm{NO}^{+}\)

Draw electron-dot structures for the following molecules, which contain atoms from the third row or lower: (a) \(\mathrm{SbCl}_{3}\) (b) \(\mathrm{KrF}_{2}\) (c) \(\mathrm{ClO}_{2}\) (d) \(\mathrm{PF}_{5}\) (e) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (f) \(\mathrm{SeCl}_{2}\)

Identify the correct electron-dot structure for \(\mathrm{XeF}_{5}{\underline{\phantom{xx}}}^{+}\).

Draw an electron-dot structure for the hydronium ion, \(\mathrm{H}_{3} \mathrm{O}^{+}\), and show how a coordinate covalent bond is formed by the reaction of \(\mathrm{H}_{2} \mathrm{O}\) with \(\mathrm{H}^{+}\).

Oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\), is a mildly poisonous substance found in the leaves of rhubarb, spinach, and many other plants. (You'd have to eat about \(15 \mathrm{lbs}\). or so of spinach leaves to ingest a lethal amount.) If oxalic acid has a \(\mathrm{C}-\mathrm{C}\) single bond and no \(\mathrm{C}-\mathrm{H}\) bond, draw its electron-dot structure showing lone pairs and identifying any multiple bonds.

Draw an electron-dot structure for carbon disulfide, \(\mathrm{CS}_{2}\), showing lone pairs and identifying any multiple bonds.

Draw as many resonance structures as you can that obey the octet rule for each of the following molecules or ions. Use curved arrows to depict the conversion of one structure into another. (a) \(\mathrm{HN}_{3}\) (b) \(\mathrm{SO}_{3}\) (c) SCN

Draw as many resonance structures as you can for the following nitrogen- containing compounds. Not all will obey the octet rule. Use curved arrows to depict the conversion of one structure into another. (a) \(\mathrm{N}_{2} \mathrm{O}\) (b) \(\mathrm{NO}\) (c) \(\mathrm{NO}_{2}\) (d) \(\mathrm{N}_{2} \mathrm{O}_{3}\left(\mathrm{ONNO}_{2}\right)\)

Draw as many resonance structures as you can that obey the octet rule for phenol \(\left(\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}\right) .\) Use curved arrows to depict the conversion of one structure into another.

Draw an electron-dot structure for carbon monoxide, \(\mathrm{CO}\), and assign formal charges to both atoms.

Assign formal charges to the atoms in the following resonance forms of \(\mathrm{ClO}_{2}^{-}\) :